When the stamp tears on demold 3, fix Shore and depth first
Soap logo tears on demold? Shore A bands, stamp depth in mm, CP vs melt-and-pour, loaf vs cavity bars, MOQ 50, prototype 3-7 days from RUUIPON Shenzhen.
Kyler Yang · Founder5 min read
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We see the same email a lot: brand mark looks sharp in CAD, then the third cold process pull rips the letter islands out of the cavity. Acrylic loafs cannot hold a face logo. Hard plastic OEM trays lock mild undercuts. Tin hobby kits smell and tear after a handful of lye pours.
Platinum-cure custom silicone soap molds are what we quote for Shopify bars, hotel amenity sets, and gift lines that need a readable stamp at MOQ 50. Prototype usually lands in 3-7 days after CAD approval; production trays sit on a 2-4 week band when files are clean. Complete RFQs get Shore and depth notes back within about 24 hours.
Wax pours are a different brief - if the SKU is a pillar or melt, start from the candle mold guide or wax melt molds instead of forcing a soap Shore band onto hot wax.
Cold-process, hot-process & melt-and-pour
Same silicone compound can serve all three if Shore and wall thickness match the worst demold you actually run. Tell us the process first - CP batter, HP gel, and glycerin-heavy MP stick differently.
| Process | What fights the mold | What we tune |
|---|---|---|
| Cold-process | Alkali contact, gel phase heat, soft green soap | Platinum grade, Shore 25-35, rinse after demold |
| Hot-process | Higher pour temp, thicker scoop texture | Slightly firmer walls; avoid thin stamp roots |
| Melt-and-pour | Glycerin stick, quick set, shiny face pulls | Draft on logos; light release if needed |
Shore A by bar geometry
Soft silicone peels stamps; too soft and a wet multi-cavity sheet folds when you twist. Pick the band for the worst bar you ship, not the Instagram pour.
| Bar type | Shore A | Why |
|---|---|---|
| Deep logo / botanical stamp | 25-30 | Peel without tearing letter roots |
| Standard guest / retail bar | 28-35 | Balance detail and tray stiffness |
| Tall loaf liner / thick slab | 30-40 | Hold shape while batter is soft |
| Dense hotel amenity sheet | 30-40 | Sheet does not flop on demold |
Broader table: Shore hardness guide.
Logo & stamp depth
Soap brands want a readable brand mark on every bar. Depth has hard limits: too shallow and the stamp washes out after 20 washes; too deep with zero draft and you tear letter islands on demold 3.
- Typical logo depth: 0.4-1.2 mm for most retail faces.
- Stroke width: keep thin strokes ≥ ~0.6-0.8 mm at the cavity face or they fill poorly in CP.
- Draft: 1-3° on deep stamp walls when height exceeds ~1 mm.
Shop note from a recent amenity sheet: artwork asked for 1.8 mm stamp depth on 0.5 mm strokes. We cut depth to ~0.9 mm, added 2° draft, and dropped Shore from 40 to 28. Scrap on demold went from every other bar to rare edge chips.
Chocolate logos run shallower for temper shine - different numbers in the chocolate guide.
Loaf liners vs individual cavities
Loaf liners cut and stamp later. Cavity bars demold as finished faces. Hotels and gift sets usually want cavities; kitchen CP makers often start with a custom loaf wall, then move to multi-cavity when volume rises.
| Format | Best for | Watch-outs |
|---|---|---|
| Loaf liner | Batch CP, swirl shows, cut to size | Wall height + corner radius; no face logo |
| Single cavity | Prototype, large statement bars | Labor per pour |
| Multi-cavity sheet | Amenities, gift sets, MP speed | Spacing + frame stiffness - see cavity layout |
Undercuts, embeds & two-part shells
Soft Shore forgives mild undercuts that would lock a hard plastic tray. Deep undercuts for "gem" embeds or interlocking shapes still need draft or a two-part shell - otherwise you stretch cavities until logos smear.
Wall thickness, glycerin & mold life
- Cavity walls 2.5-5 mm for most bars - under ~2 mm tears at stamp roots.
- Frames 4-8 mm on amenity sheets so trays do not flop under wet CP.
- Rinse alkali and glycerin residue; store flat; do not pry with metal knives.
- Detail: wall thickness guide · platinum vs tin.
DFM rules on soap quotes
- Name process (CP / HP / MP), pour temperature, and demold timing.
- Send logo artwork with intended depth - we will push back if strokes are too thin.
- Prototype before dense amenity sheets.
- Cost stack: custom silicone mold cost.
Silicone vs acrylic loaf & plastic OEM
| Path | Wins when | Loses when |
|---|---|---|
| Acrylic loaf | Straight walls, swirl photography, low tool cost | No face logo; scratches; no flex demold |
| Hard plastic OEM | Huge identical runs, simple shapes | High MOQ; weak on undercuts & stamps |
| Platinum silicone | Brand faces, MOQ 50, mild undercuts, multi-cavity sheets | Not a steel plant path for millions of bars |
Manufacturer overview: RUUIPON manufacturer page.
RFQ checklist for soap molds
- STEP/STL or photos with mm length × width × height
- Process: cold-process, hot-process, or melt-and-pour
- Logo / stamp artwork and target depth
- Loaf liner vs individual cavities; cavity count intent
- Documentation needs (food-contact / skin-contact / none)
- Prototype first? Launch or gift-set date?
Contact RUUIPON · [email protected] · WhatsApp +86 135 3006 2969.
FAQ
What Shore A is best for custom silicone soap molds?
Most logo bars and guest sizes land in Shore A 25-35. Soft 25-30 peels deep stamps and mild undercuts. Firmer 30-40 keeps multi-cavity sheets from flopping when you unmold wet CP batter.
Will platinum silicone survive cold-process lye?
Yes for normal soap-room pours. We use platinum-cure grades rated for typical CP temperatures and brief alkali contact. Do not store molds full of uncured batter for days, and rinse after demold.
What is the MOQ for custom soap molds?
MOQ 50 mold pieces per design. Brands usually prototype in 3-7 days after CAD approval, then order production trays for gift-set or hotel runs.
How deep should a soap logo be?
Often 0.4-1.2 mm depending on stroke width and Shore A. Deeper than ~1.5 mm with zero draft traps batter and tears faces. We set depth on the quote after we see the artwork.
Do soap molds need FDA or LFGB?
Soap is not always regulated like chocolate. Retail and hotel buyers still ask for food-contact or skin-contact documentation. Say the market on the RFQ so we pick compound and papers that match.
Why does my soap stick or tear the logo?
Usually Shore too hard, logo too deep with no draft, demolding while the bar is still soft, glycerin-heavy MP without a light release, or walls under ~2.5 mm at stamp roots.
How fast is a soap mold prototype?
Typically 3-7 business days after CAD approval. Complete RFQs usually get Shore, logo-depth notes, and pricing within 24 hours.
What files should I send for a soap mold quote?
STEP/STL preferred. Clear photos with mm length/width/height work. Include process (CP/HP/MP), logo artwork, cavity count goal, and whether you need loaf walls or individual bars.
Ready to order custom silicone molds?
Free quote for OEM/ODM projects. MOQ 20 · Prototype 3-7 days · FDA/LFGB available.