Tin-Cure RTV Shrink in Storage vs Size Hold | RUUIPON

Tin-cure (condensation-cure) RTV keeps shrinking after you demold. Byproducts leave for weeks, and the cavity can still walk in storage. Platinum (addition-cure) typically takes about 0.1–0.3% linear change after a full cure and then holds if you store it sane. If you signed a size from the first tin dump and then shipped goods six months later from the same tool, the SKU moved. That is chemistry, not a cheap scale.

RUUIPON will still pour tin when the master is dirty, the run is short, and you write drift on the PO. Shop in Bao'an / Shajing since 2018. Prototype 3–7 business days after CAD lock. Production MOQ 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies. Mix 1:1 or 10:1 by weight on platinum grades; tin is often 10:1. LSR shrink bands (~2–3%) are a parts plant — wydsilicone.com.

Does not apply when you already locked a platinum food tray and only want the 177.2600 pack. It also does not apply to HCR shrinkage in steel (typically about 1.5–2.5% on those compounds) — different process.

Condensation-cure keeps moving after you demold

Tin is tolerant of sulfur clay, dusty plaster, and some prints that would inhibit platinum. That is why architecture shops keep a tin drum. The trade is:

• Ongoing shrink in storage (do not treat the first dump as the locked millimetre).
• Leftover odor in wax and some resins.
• Shorter honest library life.

Platinum is the library default. Recast from the unsanded master next season and you are still in the 0.1–0.3% band. See library life and platinum vs tin.

Master compensation: if you must hit a millimetre on platinum, you cut the master with that 0.1–0.3% in mind. You cannot "compensate" tin for six months of unknown storage. Sibling: shrink compensation on the master is a different intent.

flowchart TD
  A[Need a mold this year and next] --> B{Library size?}
  B -->|yes| C[Platinum; ~0.1-0.3% after full cure]
  B -->|no disposable| D[Tin in play]
  D --> E[Write drift accepted on the PO]
  C --> F[Store keys unloaded; witness before next lot]
  E --> F

The photo that would prove the walk: a caliper on dump 1 and dump 40 after storage, same tin tool, diagonal off. We are not attaching a named PO.

Humidity and open windows change how fast tin byproducts leave, which is why two shops disagree on "how much it moved." That disagreement is a reason to leave tin, not a reason to average their guesses onto your CAD.

A platinum spare poured later from the same unsanded master will not match a tin cavity that has been walking. Do not mix twins of different chemistries in one SKU bin. Tag chemistry on the jacket.

If purchasing wants one number for "silicone shrink" across RTV, HCR, and LSR, stop. Those bands are not interchangeable (platinum RTV ~0.1–0.3%, HCR often ~1.5–2.5%, LSR often ~2–3% as typical shop values on those processes). ISO 3302-1 M2 as a drawing class still needs a chemistry that holds. M2 plus tin plus a year on the shelf is a fight.

Platinum 0.1–0.3% is a post-cure band, not a tin promise

Do not print 0.1–0.3% on a tin carton. Do not mix leftover tin into a platinum recast to "use it up." Contamination and shrink both go the wrong way.

Food: we would not spec tin. Name 21 CFR 177.2600 on the article.

Measure the CTQ after storage, not only at demold

Witness dump at demold, at full cure, and after a storage interval you care about. Table headers: date, chemistry, CTQ millimetres, notes. Typical platinum stays in band. Tin may not. We do not invent weeks-to-millimetres here.

Shop numbers for the two shrink stories

Caption: typical shop values, not a named PO.

Tin uses we would not hide

We would not recommend tin as cheaper platinum for a resin jewelry line you recast.

We would not recommend signing a chocolate size from a tin first dump.

We would not recommend storing tin and platinum keys in the same dirty bin (contamination).

We would not recommend sanding a tin cavity to "bring size back." Recast in platinum from the master.

A tooling charge is not unrestricted ownership of a dimension that the chemistry will not hold. If you need millimetres next year, pour platinum now even if tin would copy the dirty master faster — seal the master instead.

Odor is a shrink cousin: tin leftover in wax is a customer return, same as a size miss. Write both on the disposable PO so marketing does not reopen the tool as a library scent-free line.

Worked example: tin tile that would not match six months later

Architectural tile, dirty plaster master, tin glove, first dump signed. Six months later the diagonal was off and the buyer wanted a matching second batch. We sealed a copy of the master, poured platinum 20A with a plaster jacket, CAD-locked the outline (USD $50 3D applied from photos). Prototype 3–7 business days after lock. Production MOQ 20 of the platinum design. The tin original stayed a disposable. Related: concrete.

Mix-up: measuring the first dump and locking the SKU

On tin, that measurement is a snapshot. On platinum, after full cure, it is much closer to a library number. The other mix-up is compensating CAD by a guessed percent on tin as if it were LSR 2–3%.

Questions that keep size honest

• Platinum or tin, and why?
• Will you recast next season?
• CTQ millimetres — which dump generation is the sign-off?
• Storage months before the next lot?
• Unsanded master custody?

Related: contact, best silicone.

RFQ copy-pack — shrink in storage

Paste into [email protected]:

Object: RTV mold I pour into, not an LSR/HCR part Chemistry: platinum (library) / tin (disposable + drift accepted) CTQ millimetres and which dump signs them Storage months before next lot Dump and peak °C File: STEP / STL / photos with a millimetre scale CAD: mold-ready STEP OR USD $50 3D if that scope applies Prototype 3–7 business days after CAD lock, then MOQ 20 per design Platinum shrink band ~0.1–0.3% after full cure — not a tin promise

Send whether this is a library SKU. We will not lock millimetres on drifting tin — not a blank "free quote." Phone +86 135 3006 2969. Licheng Technology Industry Park, Xinhe Blvd, Shajing, Bao'an. Shop since 2018.

FAQ

How much does tin shrink in six months? It keeps moving; we will not invent a percent. If millimetres matter, pour platinum.

Can I offset the master to cancel tin storage shrink? You can offset a known platinum band. You cannot offset an unknown storage walk.

Is 0.1–0.3% a warranty? It is a typical shop band after full platinum cure, not a named lab report.

Will a jacket stop tin from shrinking? A jacket stops sag. Chemistry still moves.

If I paid for a tin tool, can you recast it in platinum? Yes if the unsanded master exists. A tooling charge is not unrestricted ownership of that master — write custody.