Unit 8: Slipcovers and Simple Upholstery

Mapping a Chair Before You Cut a Thing

A slipcover is not a bedsheet thrown over a couch. It is a garment made for a piece of furniture, and like any garment it fits only if you understand the body first. The hour you spend with a tape measure and a notebook is the hour that decides whether the finished cover hugs the arms or sags off them by Thursday.

Read the Furniture as a Set of Panels

Sit down in front of the chair and look for its seams. Almost every upholstered chair was built from flat panels sewn together: an inside back, an outside back, a seat deck, two inside arms, two outside arms, two arm fronts, a front skirt band, and a cushion. Those seam lines are the map somebody else already drew for you. Your slipcover pieces should follow them. When your seams land where the original seams land, the cover breaks and folds where the chair already wants to break and fold, and the eye reads it as tailored rather than draped.

Run your hand along each seam and name the panel out loud. Sketch the chair from the front, from the side, and from the back on three sheets of paper — crude boxes are fine — and label every panel you found. You are building a parts list, and nothing gets cut until the parts list is complete.

Let the Tape Lie Down

Here is the single mistake that ruins more slipcovers than any other: the tape measure lifts. A flexible tape stretched from the top of the inside back down to the seat wants to bridge across the hollow where back meets deck. It will take the shortcut, and it will hand you a number that is short by two or three inches. That shortfall shows up as a cover that cannot be pulled down over the arms.

So keep the tape flat against the fabric the whole way, and let it dive into every hollow and ride over every curve. On a rolled arm, walk the tape over the roll rather than across the chord of it. Where a panel disappears into the crack between the deck and the inside back, push the tape down into that crack until it stops, and add that buried depth to your number. Measure each panel at its widest point, not at a convenient point, and write the number down the second you read it. Measure everything twice; furniture is not symmetrical as often as you would hope, and a chair that has been sat in for fifteen years may be a full inch wider on the side where somebody always got up.

Tuck-In, Seam Allowance, and the Notebook

Every panel that meets another panel in a crevice needs extra fabric to be stuffed down into that crevice and anchored there. Six inches of tuck-in on the inside back and on each inside arm is generous and honest; it is what keeps the cover from creeping up when someone sits down hard. Add that six inches before you add anything else.

Then add seam allowance. Upholstery work is commonly cut with a full inch of seam allowance rather than the narrower amounts used on clothing, because heavy fabric frays freely, seams take real strain, and the extra width gives you room to correct a fit that comes out tight. Write your finished panel size and your cut size in two separate columns so you never confuse them at the cutting table.

Where It Goes Wrong

If the cover will not seat down onto the frame — the tuck-in stops short of the crevice and the whole thing rides high — the tape lifted across the hollows and every panel came out two or three inches short. If it is tight only across the seat front, you forgot tuck-in. If one arm fits and the other does not, you measured one arm and assumed the pair. If you cannot work the cover past the arms at all, you measured the arm at its narrowest point rather than its widest.

None of these are recoverable after cutting, and all of them are cheap to prevent. Proverbs says the prudent man looks well to his going. A tape measure is a small tool for looking well, and careful measuring is not fussiness — it is a plain kind of honesty about what is actually in front of you rather than what you assumed was there.

Choosing Cloth That Will Outlast the Chair

Fabric choice decides more about a slipcover than your stitching ever will. A beautiful cover cut from thin, loosely woven cloth will pill on the seat front and split at the arm seam inside a year. A plain cover cut from honest cloth will still be serving your family when the chair under it needs new legs.

Weight, Named in Ounces

Cotton canvas and duck are sold by weight per square yard, and the number is a reliable shorthand for how the cloth will behave. Light canvas runs around 7 ounces. Medium sits in the 8 to 10 ounce range. Heavy canvas is 12 to 14 ounces. The familiar heavy-duty numbered duck called #12 falls at about 11.5 ounces and is woven from two-ply yarns, which is part of why it wears so well — a two-ply yarn resists abrasion better than a single of the same thickness.

Match the weight to the use, not to your ambition. A chair in a guest room that hosts company twice a year is perfectly served by an 8 or 9 ounce cloth, which is far easier to sew, presses flatter, and does not fight the machine at every seam intersection. The chair by the wood stove where three children pile in after chores wants 12 ounces or better. Going heavier than you need is not a virtue; it makes bulky seams, dulls needles, and produces a cover so stiff it will not tuck into the crevices.

Weave, and Why Tight Beats Loose

Weave is the interlocking of warp yarns, which run lengthwise, with weft yarns, which run crosswise. Hold a candidate fabric up to a window. If you can see daylight freely between the yarns, the weave is open, and open weaves fail in the ways that matter here: they fray at every cut edge, they let seam threads pull through under load, and they grow baggy where a body sits. A tight weave is stronger and more durable than a loose one of the same fiber and weight. Scratch a corner hard with your thumbnail; if yarns shift and leave a smear of distorted weave, put the bolt back.

The selvedge — the finished edge the loom made — runs parallel to the lengthwise grain and is your permanent reference for direction. Never cut it away before you have marked your grain lines.

Prewashing Is Foresight, Not Fussiness

Cotton and cotton blends shrink, and they shrink most in the first wash. A slipcover exists to be washed. If you sew it from unwashed cloth, the first laundering will pull it two or three percent smaller in both directions, which on a seventy-inch sofa panel is enough that the cover will no longer reach the tuck-in crevice. It will never fit again, and there is no repair for it.

So wash and dry the yardage exactly the way you intend to wash the finished cover — same water temperature, same dryer heat — before a single piece is cut. Do it twice if the fabric is a heavy cotton and you want to be certain. Press it flat afterward, because you cannot cut accurately on wrinkled goods. This is the plainest possible application of the proverb: a prudent person foresees the trouble and steps aside from it, while the simple walk straight into a cover that shrank off the furniture.

Pattern, Color, and Honest Expectations

Solid colors and small all-over textures are forgiving; stripes, plaids, and large repeats are not, because every panel must be cut with the motif squared and matched at the seams, and that can add a third again to your yardage. If this is your first slipcover, buy a solid.

Choose color for light and for dirt. A very pale cover in a room with an outside door will read as gray at the seat front within a season. A mid-tone with some texture hides the ordinary business of a family without looking soiled.

Finally, buy the whole project at once from the same bolt. Dye lots differ, and a replacement panel cut months later from a second bolt will not match under window light, however close it looks in the store.

Grain Lines: Lengthwise, Crosswise, and the Useful Bias

Woven cloth is not a uniform material. It behaves in three distinct ways depending on which direction you pull it, and a slipcover that ignores those directions will twist on the furniture no matter how carefully it was measured. The robe of the ephod was made of woven work, and woven work has always obeyed its own rules. Learn them once and they serve you for every project you ever cut.

Three Directions, Three Behaviors

Take a square of canvas about a foot on a side and pull it three ways.

Pull along the lengthwise grain, parallel to the selvedge. It barely gives. Lengthwise yarns are held under tension on the loom and are the most stable direction in the cloth. This is where you want the length of any panel that carries weight or must hang straight.

Pull along the crosswise grain, from selvedge to selvedge. There is a little give — moderate stretch, enough to notice under your hands. Crosswise is fine for panel widths and for pieces that need to ease slightly over a curve.

Now pull at 45 degrees to both, corner to corner. That is the bias, and the cloth stretches generously and springs back. Bias is the direction that lets flat fabric go around a curve without wrinkling. It is why piping strips are cut on the bias and why curved slipcover edges are faced or bound with bias-cut strips.

Finding Grain Honestly

Do not trust the cut edge from the store; it is almost never square. Snip through the selvedge an inch and tear across, or pull a single crosswise yarn free and cut along the track it leaves. Either method gives you a true crosswise line. Fold that line back on itself with the selvedges aligned. If the fabric lies flat with no diagonal ripple, the piece is on grain. If a diagonal wrinkle runs corner to corner and will not press out, the cloth is off grain, meaning the weave was pulled askew during finishing. Tug it firmly on the opposing bias and press with steam until the fold lies flat before you cut.

Mark grain lines on your paper pattern pieces with a long arrow and lay every piece with that arrow parallel to the selvedge. It takes twenty seconds and it is the whole discipline.

Why This Shows Up on the Chair

A seat deck cut off grain will look fine on the table and then pull to one side once someone sits on it, because the weight loads the bias direction and the bias moves. Hems cut off grain angle instead of running level. A cover whose panels are cut in mixed directions catches light differently panel to panel, and even in a solid color you will see faint blocks of lighter and darker cloth.

With stripes and plaids the penalty is unmistakable. A stripe follows the yarns, not your cutting line, so if the panel is off grain the stripe runs downhill across the chair back and everyone who enters the room will see it. Cut all major panels with the pattern running the same direction, and match the motif across every vertical seam.

Napped and Directional Cloth

Velvets, corduroys, and brushed cottons have a nap that lies one way. Run your palm up and down a piece; one direction feels smooth and reflects light pale, the other feels rough and reads dark. Every panel must be cut with the nap running the same way, usually downward on the finished piece so dust and hands sweep with the pile rather than against it. Cutting one arm with the nap reversed produces a chair that appears to be two different colors, and no amount of pressing will fix it.

Fixing What You Can Still Fix

If you discover an off-grain panel before assembly, recut it; canvas is cheaper than the hours ahead of you. If a finished cover twists on the furniture, check the seat deck and inside back first, since those two carry the load. Grain trouble is one of the few sewing faults that cannot be steamed, eased, or pressed away, which is exactly why it is worth five careful minutes at the cutting table.

Needle, Thread, and Seams That Hold Under Weight

Every slipcover fails at a seam before it fails anywhere else, and it fails at the seam that carries the most movement — usually the front of the seat or the joint where the inside arm meets the deck. Those few inches of stitching are the feeble members that the whole cover depends on. Set the machine up for them deliberately.

Matching Needle to Thread

The needle's job is to open a hole large enough that the thread passes through the fabric without being scraped raw by it. The working rule is that the eye of the needle should be roughly forty percent larger than the diameter of the thread. Undersize the needle for the thread and you get skipped stitches, shredded thread, and eventually a broken needle. Oversize it badly and you punch visible holes in the cloth.

For medium-weight upholstery fabric and for topstitching, a size 90/14 needle is the standard choice. Lighter home-decorating cottons are often happier with an 80/12. Heavy canvas and multiple layers may want a 100/16, and a needle sold specifically for denim or jeans has a stout shank and a sharp point that pushes through dense weave without deflecting.

Thread is measured in Tex, where a higher number means a thicker thread. Tex 70 is about as heavy as most household machines will feed and tension reliably; that is the practical ceiling for the machine on your table. Tex 90, sometimes labeled B92, is the ordinary working weight in upholstery shops with industrial machines. Before you buy a cone of anything heavy, look in your machine manual for a stated maximum, because forcing thick thread through a light tension assembly and a small bobbin case is how feed dogs and hooks get damaged.

Test on a Folded Scrap First

Never make your first stitch of the day on the project. Fold a scrap of the actual slipcover fabric so the sample has as many layers as the thickest place in the real seam — often four layers where two seam allowances cross. Sew a few inches.

Lengthen the stitch from whatever you use on quilting cotton. Heavy cloth needs a longer stitch, because a short stitch perforates the weave so densely that the fabric can tear along the stitching line like a postage stamp. The right length is the one that looks right on your sample: the stitching lies flat, the fabric is not gathered, and no loops show on the underside. Your machine and your fabric decide the number together, so read the sample rather than a chart. Check the tension on the same piece — loops underneath mean the top tension is too loose or the machine is not threaded through the take-up lever properly.

Fingers stay well behind the needle when you feed thick goods. A needle striking a pin or a bulky seam intersection can snap and throw a piece, and hands close to the presser foot are how that becomes an injury. Slow the machine down and use the handwheel over the thickest crossings.

Finish the Raw Edges

Cut edges of upholstery-weight cloth fray freely, and once a seam allowance has frayed back to the stitching line the seam is finished. Zigzag or overcast each raw edge before assembly, while the pieces are still flat and easy to handle. A medium-width zigzag worked along the edge is enough; the point is only to lock the yarn ends.

Where a seam takes real strain — the seat front, the arm-to-deck joint, the corners of a boxed cushion — sew the seam twice. Lay the second line about an eighth of an inch inside the first, in the seam allowance. It costs a minute and it doubles what has to fail before the seam opens.

Reducing Bulk Without Weakening

Upholstery seam allowances are generous, commonly a full inch, and a full inch of heavy canvas folded into a corner makes a hard lump that shows through the cover. Trim the allowance back after the seam is sewn and tested, but trim it in steps rather than all at once, and never trim closer than about three eighths of an inch. Clip into the allowance on inside curves so the seam can open and lie flat, and notch small wedges out of outside curves so the layers are not fighting each other. Press every seam before it crosses another one; a pressed seam is half a seam better than an unpressed one, and it is the difference an experienced eye notices immediately.

The Ladder Stitch: Closing a Seam So Nothing Shows

Sooner or later you will have an opening that cannot be closed by machine. A cushion cover stuffed through its own gap, a chair arm split along an old factory seam, a slipcover corner turned right side out through a hole you left on purpose — all of them need a hand seam that disappears. The ladder stitch does exactly that, it needs no machine setup at all, and once your hands know it you will use it for the rest of your sewing life.

What the Stitch Actually Does

Look at the opening. Both raw edges are turned to the inside along the same line the machine seam would have followed, so you have two folded edges facing each other with a narrow channel between them. The ladder stitch runs the thread back and forth across that channel, taking a short bite inside one fold, then a short bite inside the opposite fold, then back again. Seen before it is drawn up, the thread makes little horizontal rungs between the two folds, which is where the name comes from. When you pull the thread, the rungs vanish inside the folds and the two edges come together with no thread visible at all. It is also called the invisible stitch or slip stitch.

Working It

Press first. A crisp pressed fold gives you a line to follow, and hand sewing along a wandering fold will never look straight. Use a single strand of thread that matches the fabric, knotted at the end, and bury the knot by entering inside one fold so it never shows.

Bring the needle out through the fold, cross the channel, and enter the opposite fold directly across from where you came out. Travel inside that fold about a quarter inch, come out, cross back, and enter the first fold directly opposite again. Keep the bites no wider than a quarter inch. Longer bites go faster and look worse, because the fabric between them can gape open under any strain.

Work about an inch of loose rungs, then draw the thread up. Snug, not tight — the folds should meet and lie flat, and that is all. Pulling hard is the classic beginner error; it gathers the seam into a puckered ridge, and no amount of pressing will take that ridge out. If you see the fabric bunching, back the tension off and redo the inch.

At the end, take two small backstitches inside a fold, run the needle an inch away through the fold, and clip the thread where it emerges so the tail withdraws inside.

Where It Goes Wrong, and the Fixes

Visible thread across the surface means the needle entered outside the fold rather than inside it. Take those stitches out and re-enter under the fold line. Stitches that show as small dimples along a straight seam usually mean the bites are catching too many layers; take a shallower bite.

A gap that reopens after a few weeks of use is a sign the stitch was doing structural work it was never meant to do. The ladder stitch is a closing stitch, not a load-bearing one. If the opening is on a cushion boxing seam that a body sits against, close it by hand for appearance but understand you may need to open it and machine-stitch through both layers if it keeps failing.

On a repair to a seam that split on existing furniture, first check why it split. A cushion cover seam that opened because the foam beneath it swelled will simply open again after you sew it. Deal with the cause, then close the seam.

A Word on Small Repairs

There is real dignity in mending. A split seam caught at a quarter of an inch takes four minutes with a needle; the same split left for a month becomes a six-inch tear through weakened cloth and a much larger job. Paul writes that there should be no schism in the body, but that the members should have the same care one for another. It is a picture of the church, and a plain worker will recognize it in her own hands: seams tended early hold together, and care given to the small joint keeps the whole from tearing.

Patching Holes and Tears in Existing Upholstery

A cigarette burn, a cat's work on a chair arm, a small tear where a spring pushed through — none of these justify recovering a whole sofa, and all of them can be made to disappear well enough that a guest never notices. The method is a patch worked from the back of the fabric, not the front, so no stitching or edge ever shows.

Gather Your Fragments

Where does patching fabric come from? From the furniture itself. Nearly every upholstered piece hides usable cloth somewhere: under the deck at the back where the cover wraps out of sight, on the underside of a cushion boxing, inside a skirt hem, or in the tuck-in that vanishes into the crevice. Take the patch from a place no eye reaches, and the repair matches perfectly because it is the same cloth, faded by the same years of the same light. When you make a slipcover or a cushion cover, save every offcut in a labeled bag for the same reason — gather up the fragments, that nothing be lost.

If you must use new fabric, hold candidates against the damaged area in daylight, not under a lamp. Color that matches under a bulb frequently does not match by a window.

Prepare the Hole

Trim the damage back to sound fabric. Snip away scorched, brittle, or badly frayed yarn ends with small sharp scissors so the opening has a clean boundary; a ragged edge telegraphs through any repair. Keep the removal to the minimum that gets you to strong cloth.

Now cut the patch. It goes behind the hole, so cut it to the size of the opening plus a small margin — enough to underlie the edges rather than butt against them. Then cut a second, plainly larger piece as a backing that will extend well past the first in every direction. Two layers do two different jobs: the first fills the visible gap, the second holds everything to the surrounding fabric.

Match the Weave Direction

This is the step people skip and then wonder why the repair opened again. Set the patch into place with its weave running the same direction as the fabric around it — lengthwise yarns parallel to lengthwise yarns. A patch turned ninety degrees will stretch differently than its neighbors under every sitting, and the two will work against each other until the joint separates. It also catches light differently, so a crosswise patch shows as a faint bright square even in a solid color.

Before you commit, slide the patch in and look at it from a standing position across the room. That is the distance from which it will be judged.

Setting It In

Work the patch through the hole and flatten it under the face fabric, right side up, so its edges tuck beneath the edges of the opening all the way around. Use a blunt tool — a butter knife, a small crochet hook — to coax the corners into place without snagging.

Apply fabric glue sparingly to the underside of the face fabric around the opening, and press the patch to it. Sparingly is the whole instruction; glue that soaks through to the front dries stiff and shiny and is far more visible than the original hole. Then glue the larger backing piece over the first from behind, so it laps onto sound fabric all around.

Weight the repair flat with a book on a piece of waxed paper and leave it until the glue has fully cured according to its own label — read the container, since products differ, and do not sit on the chair before then.

If your patch fabric is one that takes an iron-on adhesive, that route is cleaner still: place the fusible web between the patch and the fabric and press it with the iron, using a press cloth so nothing sticks to the soleplate. Test the heat on a hidden scrap first, since upholstery fabrics of unknown fiber can glaze or scorch.

Fabric glues and spray adhesives often carry solvents. Open a window, keep them off your skin, and keep the can and the hot iron away from children who wander into a sewing room.

Setting Expectations

A well-made patch on a low-wear surface — an outside arm, a back panel — can be genuinely invisible and last for years. A patch in the middle of a seat cushion sits under a body's full weight every day and will need looking after. Judge the location before you judge the method.

Making Your Own Piping from Bias Strips

Piping is a cord wrapped in a strip of fabric and sewn into a seam so a firm, defined edge runs along it. It is the detail that separates a homemade-looking cover from a made one. It does honest structural work too, because the cord takes the abrasion at the outside corner instead of the seam thread. And it is the one place in a plain slipcover where a second color belongs — Joseph's coat of many colors is a reminder that beauty in cloth is an old and blessed thing, and a length of contrasting piping is a modest and inexpensive way to give a room some life.

Cut the Strips on the Bias

Piping strips must be cut on the true bias, at 45 degrees to the lengthwise and crosswise yarns. On the bias the covered cord can bend around an arm front or a cushion corner and lie smooth. A strip cut on the straight grain will not bend; it wrinkles into hard ripples on every curve, and there is no fixing it once sewn.

Find the bias by folding a cut crosswise edge up to meet the selvedge. The diagonal fold that forms is the true bias. Press that fold, open it out, and mark cutting lines parallel to it with a long ruler.

How wide? Measure the circumference around the cord itself, add two seam allowances, and cut to that. For common cotton cording of about a quarter inch diameter, a strip near two inches wide is comfortable and gives room to trim later. Cut wider rather than narrower; a too-narrow strip leaves nothing to sew through.

Joining Strips

You will never get enough length from a single bias strip. Join them end to end with the seams themselves on the straight grain: lay two strips right sides together at a right angle so their ends cross, stitch across the diagonal, trim the allowance, and press the seam open. Pressing that little seam open matters, because a seam pressed to one side makes a lump inside the finished piping that shows as a bulge on the finished edge.

Wrapping the Cord

Lay the cord down the center of the strip, wrong side of the fabric up, and fold the strip around it so the raw edges meet evenly. Fit the zipper foot to the machine and shift the needle position as far left as it will go, so the foot rides beside the cord and the needle stitches right alongside it.

Sew the length of the piping, keeping the cord snug in the fold but not strangled. Do not crowd the stitching hard against the cord on this first pass. Leave a hair of space, because when you later sew this piping into a seam you want that second line of stitching to fall closer to the cord than the first — that is what pulls the piping tight into the finished seam and buries the first stitching out of sight.

Guide the fabric with your fingers well back from the foot. A zipper foot puts the needle close to your fingertips, and thick cord tempts people to push. Let the feed dogs pull.

What Goes Wrong

Twisted piping — the cord riding to one side rather than sitting in the middle — comes from letting the strip shift as you feed. Stop every few inches, smooth the strip around the cord ahead of the needle, and start again.

Wrinkled, wavy piping on a curve means the strip was not on the true bias. Check the offcut against your bias line.

Lumps at intervals mean joining seams pressed to one side instead of open.

Puckering along the whole length usually means you stretched the bias strip as you sewed. Bias stretches easily and permanently. Feed it without pulling, and if you have already stretched a length, cut it out rather than trying to shrink it back.

Storing and Planning

Make more than you need in one sitting. Setting up the zipper foot, cutting bias, and joining strips is most of the labor, and the marginal cost of another two yards is small. Wind the finished piping loosely around a cardboard tube; tight coils crease the fabric and the crease shows when it is sewn in.

Setting Piping into a Seam and Around a Corner

Made piping is only half the job. Installing it well is what produces a crisp, even line around a cushion or down an arm front, and installing it carelessly produces a wobbling edge that draws the eye to every fault. Paul writes of laying a foundation and then taking heed how one builds on it. Your finished piping is the foundation; this is the building.

The Three-Layer Sandwich

A piped seam is three lines of stitching in the same place, each one a little closer to the cord than the last.

The first line is already there, holding the cord in its bias wrapper. The second attaches the piping to one panel. The third joins that panel to its partner. Because each line creeps inward, the earlier stitching is pulled underneath and hidden, and the cord ends up sitting hard against the finished seam with no slack.

Keep the zipper foot on and the needle as far left as it will go for all of it. Work slowly. There is no speed to be gained here and a great deal of appearance to be lost.

Basting the Piping to the Panel

Lay the piping on the right side of one panel with its raw edges even with the panel's raw edge and the cord pointing inward, away from the edge. Pin it or hand-baste it. On heavy canvas, pins slip and shift under the foot; a line of long hand-basting stitches holds better and costs five minutes.

Stitch the piping to the panel, staying just barely inside the first line of stitching — that is, a hair closer to the cord. Then lay the second panel face down on top, raw edges matched, and sew the final seam a hair closer still. When you turn the work right side out, the cord should stand up firm and round with no stitching visible.

If you can see the first stitching line on the finished edge, your last seam was not close enough to the cord. Sew again, a little tighter, and pick out the loose line.

Corners and Curves

At an outside corner, such as the front corner of a boxed cushion, the piping must turn sharply and the seam allowance underneath will not let it. Clip into the piping's seam allowance right up to — but not through — the stitching line, three or four cuts fanned out at the corner. The allowance opens like a fan, the cord swings around the turn, and the corner comes out square instead of rounded.

On a gentle outside curve, such as an arm front, snip the piping's seam allowance every inch or so. On an inside curve, the allowance is crowded rather than stretched, so clip it in the same way to let it spread. Bias-cut piping will follow the curve willingly once its allowance can move; straight-grain piping will not, no matter how much you clip.

Joining the Ends

Piping that runs all the way around a cushion has to meet itself. Stop stitching a few inches short of where the ends will meet. Trim both ends so they overlap by about an inch. Open the fabric wrapper on one end, expose the cord, and cut that cord so the two cord ends butt together exactly. Fold the raw fabric edge of the open end under about half an inch, wrap it around the other end so it encloses it, and stitch through everything. The join reads as a slight thickening rather than a lump or a gap.

Never simply cross the ends and stitch them down. That leaves a hard bump under the cover that you will feel every time you sit.

Common Faults

Piping that waves along a straight run means you stretched it while sewing; bias stretches, and a stretched length will not lie down. Feed it, do not pull it.

Uneven cord exposure — fat in one place and thin in another — means your stitching line wandered relative to the cord. Watch the cord, not the fabric edge, as you sew.

A rounded corner where you wanted a square one means the allowance was not clipped deeply enough. Clip closer, but stop short of the stitches, because a clip that cuts through the stitching line opens the seam.

Press the finished seam from the wrong side over a rolled towel so the cord is not flattened by the iron. Keep the soleplate clear of the cord itself; crushed piping never fully recovers.

Reviving a Sagging Cushion with Foam and Batting

A chair usually looks tired before it is worn out. The frame is sound, the fabric has years left, and what has actually failed is a single seat cushion that has flattened into a dish. Job speaks of a neighbor warmed with the fleece of his sheep — of comfort provided by a man's own hands out of his own goods. That is exactly this work: comfort restored to a household chair for very little money and one quiet afternoon.

Judge the Foam First

Unzip the cover and take the foam out. Set it on a flat table and look at it from the side. Sound foam sits level and full. Failed foam shows a permanent depression that does not rise when the weight is gone.

Press your palm into the center. Good foam pushes back and returns promptly to its full height. Foam that has broken down feels dead, returns slowly or not at all, and often crumbles at the edges into yellow dust when you rub a corner. Once the cell structure has collapsed, no amount of wrapping will bring it back — batting over dead foam gives you a soft lump, not a cushion. Replace it.

If the foam is sound and the cushion is merely loose in its cover, batting alone will solve the whole problem.

Cutting Replacement Foam

Buy foam the same thickness as the original and firmer than you think you want, because the batting and the cover will both soften the feel. Use the old foam as your pattern: lay it on the new slab, trace around it with a marker, and cut with a long serrated blade — an electric carving knife or a long bread knife — held vertical, using the full stroke rather than sawing in short jabs. Short jabs produce a ragged, angled edge. Cut just outside your line; foam compresses under the blade and a cut made exactly on the line comes out small.

A cushion should be cut slightly larger than the finished cover, not smaller. Foam that is a half inch generous fills the cover's corners and keeps the boxing standing upright. Foam cut undersize leaves hollow, dog-eared corners that no cover can disguise.

Keep blades away from the edge of the table and keep children out of the room while a carving knife is running.

Wrapping the Batting

Polyester batting, often called Dacron in upholstery work, is what turns a hard rectangle of foam into something that looks upholstered. It fills the small gap between foam and cover, rounds the edges, and stops the cover from creasing along the foam's sharp corners.

Cut a piece long enough to wrap three surfaces — up the front, across the top, and back underneath — leaving the two ends of the cushion bare, which are where the boxing seams sit. One layer is enough for a firm modern look. Two layers give a plumper, more traditional shape. Hold the wrap in place while you work: a light spray adhesive between foam and batting works, and so does hand-tacking the batting to itself with a few long stitches. Either holds well enough; choose by what you have and what you can ventilate, since spray adhesive needs an open window.

Smooth the batting flat with your palms as you wrap. Wrinkles and folded-over lumps do not disappear under the cover — they read as ridges across the top of the seat, and they are the most common complaint about a first attempt.

Getting It Back in the Cover

A properly stuffed cushion does not slide into its cover; it has to be persuaded. Squeeze the wrapped foam narrow, feed the far end in first, and work the cover down over it. Slip a large plastic bag over the batting to let the cover slide, then pull the bag out through the zipper opening once the foam is seated.

Reach in and square each corner of the foam into each corner of the cover before you close the zipper. Then stand the cushion up and look at the front edge. It should be full and straight. If it dips, a corner is not seated. Open it and fix it now, because a cushion put away wrong will keep its wrong shape.

Installing an Invisible Zipper So the Cover Comes Off

A cushion cover that cannot be removed is a cushion cover that cannot be washed, and an unwashable cover on a family's chair is a cover with a short life. The invisible zipper solves this. Its teeth are a coil carried on the reverse side of the tape, so when the zipper is closed the seam looks like an ordinary seam and only the small pull shows. The best work in a house is often the work nobody sees, and the Psalmist's marvelous works are wrought where no eye follows them. A hidden zipper set straight and smooth is a small piece of that.

Placement and Preparation

Put the zipper in the back boxing strip of the cushion — the strip that faces the chair back — and run it well past the two back corners, three or four inches around each side. A zipper that stops at the corners will not open wide enough to get a stuffed cushion through, which is the most common reason a finished cover has to be unpicked.

Buy the zipper a few inches longer than you think you need. Extra length is easily left hanging past the seam; a short zipper is a failure.

Interface both seam allowances where the zipper will sit. A strip of lightweight fusible interfacing about an inch and a half wide, ironed to the wrong side along each allowance, keeps the cut edge from stretching as you sew. Without it the seam ripples along the zipper and there is no pressing that out. Use a press cloth so no adhesive reaches the soleplate.

Press the zipper tape before you begin. A coil zipper comes out of the package with its coil curled toward the tape. Open the zipper, lay it face down, and press the coil flat with a warm — not hot — iron so the coil stands up and the tape lies open. This one step does more for the finished result than any other. Test the heat on the tape end first; synthetic tape will glaze under an iron that is too hot.

Stitching It In

Work with the zipper open and one side at a time. Lay the open zipper face down on the right side of one seam allowance, coil aligned along the seam line, tape toward the raw edge, and pin or baste.

Fit an invisible zipper foot if you have one; the grooves on its underside ride over the coil and hold it upright. A regular zipper foot will do the job if you keep the coil rolled back with your fingertip ahead of the needle.

Stitch as close alongside the coil as you can get without stitching into it. The needle should pass beside the teeth, not through them. Sew from the top down, stopping when the foot reaches the slider. Then close the zipper, ease the slider past your stopping point — fingers work, and so does any small gripping tool that lets you shift it without pulling the fabric — reopen the zipper, and finish the seam.

Repeat on the second side, and match the two starting points exactly so the seam does not step at the top.

Closing the Seam Below the Zipper

Below the zipper's stopping point the seam is still open. Close it with an ordinary straight seam, beginning as close to the end of the zipper stitching as the foot allows. A visible gap where the two lines fail to meet is the mark of a rushed installation. Change back to a zipper foot for the first inch if the regular foot cannot get in beside the zipper's bulk.

Faults and Cures

If the zipper will not slide, the stitching caught the coil. Pick out the stitching in that stretch and sew again a hair farther from the teeth.

If the seam ripples along the zipper, you skipped the interfacing or stretched the allowance while feeding.

If the closed zipper shows its coil rather than hiding it, the stitching was too far from the teeth; move in.

If the cover will not go over the foam even with the zipper fully open, the zipper is too short or did not turn the corners.