Candle Undercut: Split the Mold Before You Soften the Shore
A wax piece that tears at a return needs a split, a shallower undercut, or a cooler pour. A softer Shore peels the logo and then collapses the wall. Soap is a separate tool.
On this page
The candle tears at the undercut, so someone asks for a softer mold. Soften the Shore only after you know the tear starts in a return the wax cannot pass. A split, a shallower return, or a cooler pour often releases the piece without a wall that collapses on the next pour. The candle tray quote stays on custom silicone candle molds.
Split, shallower, or softer
| Where it tears | First change | Leave alone |
|---|---|---|
| Wax locks on a lip or a deep logo return | Split the mold or cut that return back | Dropping Shore until the whole wall folds |
| The piece skins and sticks while the core is still hot | Name pour temperature and dwell. Demold later, or cool the pour | A release spray as the acceptance test |
| Only one cavity in a multi-cavity tray tears | Fix that cavity's draft. Do not recut the tray | A new Shore for every cavity |
| The mold itself rips at a thin web | Thicken the web or move the split. A softer grade rips sooner there | "Make it softer so it stretches" |
We would not recommend a Shore change as the first reply to an undercut photo. Send the tear location.
Soap is not the same demold
Soap can be heavier, cooler, and more alkaline than the wax you poured. A candle tool that releases pillar wax can lock a soap bar, or the reverse. Quote soap on custom silicone soap molds unless the RFQ says both uses and you accept two trials. Wax-melt snap bars are another geometry: wax-melt stick and snap.
What a scan does not decide
A scanned master shows the shape. It does not show pour temperature or which face has to be the split. An undercut that looks fine in a render still needs a release path. Your wax and your split can differ.
Timing on a current quote
WYD quotes from Bao'an (since 2006). Soft-mold programs often start around 20 molds per approved design. That floor is not a universal MOQ for HTV, LSR, or an industrial tool. Simple 3D modeling can start around USD 50 when the file is not ready. It is not a tooling deposit. DFM on a complete file is quoted as review, not as a second product.
- Reply: typically within 12 hours
- CAD / DFM: 1-3 business days
- Prototype: typically 3-5 business days after CAD approval
- Small batch: typically 2-3 business days after sample approval
- Standard production: typically 7-10 business days after approval
- Large or multi-insert tools: by project. Shipping is separate.
What to send
Send the wax type, pour temperature, a photo of the tear, and whether you can accept a split line on that face. If soap is also in the plan, say so. We will quote a split, a shallower return, or a Shore trial after those two are named.
Send the tear photo with the pour temperature.
FAQ
Will a softer mold always release a detailed candle?
No. Soft silicone stretches over the undercut and then tears the wax or the mold wall. Split or shorten the return first.
Can one mold pour candles and soap?
Not by default. The demold and the chemistry differ. Say both on the RFQ or expect two tools.
Does a 3D scan remove the undercut?
No. The scan copies it. Someone still has to choose the split.
Is spray an acceptable production method?
Only if you write it into the SOP and the piece still meets the surface you sell. We do not sell the spray.
Where is the candle mold quote?
On the candle molds page. This article is the undercut decision before that quote locks a Shore.
Ready to order custom silicone molds?
Send your drawing, sample or project requirements for DFM and quotation.