How thick should 3D puff foam be, and what satin settings does puff embroidery need?

Use 3 mm foam, firm (65D to 75D) for caps and soft (38D) for sweatshirts, and stitch the puff as satin columns only, spaced 0.16 to 0.18 mm apart, with no underlay inside them. That is more than twice as dense as a normal 0.4 mm satin, on purpose: the needle holes have to sit close enough to cut the foam. Below are the foam grades makers sell, the satin settings from Hatch, Madeira and a Wilcom puff webinar, and which to follow where they seem to disagree. For where puff fits among other techniques, see the 3D puff section of the projects guide.

Foam thickness and hardness by job

Foam is sold by thickness and by a density grade with a D after it. Within Würker's range, 75D is the "hard / firm" grade and 38D the "soft" one. No page here says which scale the D refers to, so treat it as a ranking within one catalog.

• Thickness: 3 mm. It is every maker's standard sheet. Use 2 mm for a lower profile and 4 mm for more loft, then stop: "A good dense 4mm foam will render a much cleaner, lofty design than the 5-6mm" (Armenta).
• Caps and crisp lettering: firm, 65D to 75D. Sweatshirts and polos: soft, 38D, which Würker says stays comfortable "instead of feeling stiff".
• Not craft foam. It "is not dense enough to support embroidery", while foam that is too dense "won't tear off as well" (Armenta).
• Match foam to thread color. Hatch, Madeira and SPSI all say it: leftover bits between stitches disappear.

The real disagreement is stacking. Würker says its soft foam layers "for a stronger 3D effect". Armenta advises against doubling 2 mm sheets: "The second layer of foam can shift during sewing, causing deflection and possible excess thread/needle breaks." Buy the height you want as one sheet.

Satin settings for puff

Satin is the rule because, as Hatch puts it, "Satin fill is the only one that has no stitches inside the object." Any stitch landing inside the column presses the foam flat there.

What the density numbers mean

Spacing in mm and points (1 point = 0.1 mm in many programs) gets lighter as the number rises; lines per inch gets denser. Lines per inch = 25.4 divided by spacing in mm, and the density converter does the rest.

Madeira prints "2.0 - 25" with no unit. It cannot be lines per inch (2 per inch is one stitch every 12.7 mm), so it is spacing in a program's own scale, and as points it is slightly lighter than the other two. Start at 0.16 to 0.18 mm and treat 0.25 mm as the light limit.

This is the one place the advice in stitch density runs backwards. Normally you open spacing until coverage is just solid. Over foam the extra holes are the point: "The penetration points must be much closer for the foam to be cut properly," Hatch writes, "so at the end you can just pull the excess foam away easily." The test is a clean tear, not coverage.

Underlay: Hatch and Madeira agree

Hatch says "no underlays are used"; Madeira says to "stitch underlay or outline stitches prior to laying down the 3D foam". They describe different stitches. Hatch means underlay inside the puff satin, which would sew on top of the foam: "Stitching underlays would push the foam down." Switch it off in every puff object, as Armenta does. Madeira means stitching sewn before the stop, onto bare fabric, which ends up under the foam and cannot crush it.

So sequence decides it. Anything that stabilizes the fabric sews before the foam goes down; after the stop, only stitches that hold or cut the foam. Hatch makes its holding run 4 mm long so it does not "push down the foam too much". If a stretchy fabric needs underlay under the puff, put it before the stop; the underlay guide covers which type.

Column width: 7 mm or 12 mm?

Hatch's 7 mm limit comes from software, not foam: it is "just a bit over the width where the Satin fill would start to split if you have the Auto split box ticked", and a split puts stitches in the middle of the column. Armenta works up to 12 mm and puts the satin limit at "typically 10-12mm max" depending on the machine. Stay at 7 mm or under unless your program and machine sew long satins cleanly (see stitch types for float limits).

The minimum matters more. Armenta's best case is 3 mm: "2mm can work, but depending on the design elements, it may compress the foam too much." That decides puff lettering by stroke width and the gaps inside letters, not letter height.

Pull compensation: start at zero

Madeira gives 5 to 15% depending on element size; Armenta uses none, because "the foam already pushes on the thread, preventing it from pulling in." His mechanism is the better guide. On flat fabric a satin narrows because tension gathers the fabric (see pull compensation); over foam the thread wraps a block that resists. Start at zero and add from the bottom of Madeira's range only if columns sew narrower than the art.

Stitch it in this order

1. Flat elements and support first. Madeira says it is "best to insert a stop in the design after the flat part of the embroidery is done and before the raised part of the embroidery is started."
2. Lay color-matched foam at the stop. Hatch sprays the corners; Madeira tapes it inside the hoop.
3. Loosen the top tension slightly. Hatch does it so "the stitching does not push the foam down." Rebalance with an I-test before the next flat job.
4. Stitch the puff and its caps. Armenta runs 3D best at 650 to 750 stitches per minute (see speed settings), with 75/11 true sharps and polyester thread, which he finds stronger over foam.
5. Tear away and tidy. Tweezers for small bits, then low heat for what still pokes out (Hatch: heat gun on low; Madeira: hair dryer). Madeira warns not to burn the thread.

Where these numbers stop applying

• Keyboard lettering. Madeira says to move stitches one at a time if needed to prevent center stitches "that would lay down the foam".
• Fills. The spacing here is for satins; Armenta says fill puff needs "specific settings" and a satin edge.
• Foam over 4 mm or columns under 3 mm. Outside every source's working range.
• A flat design. Stitched over foam, it leaves foam showing and edges that do not cut.

If edges come out ragged or foam shows, check spacing and capping before the foam; satin stitch problems covers gaps. Change one setting per sample, as the Stitch-Out Tuning Method sets out.