Shop Humidity vs Tin-Cure RTV (Not Platinum) | RUUIPON

Tin-cure (condensation) RTV needs moisture in the air to finish; a dry winter room or a sealed plastic tote can leave the face undercured while the cup heel looks fine. Platinum RTV is addition-cure: humidity is not the catalyst, so a wet shop does not "help platinum kick" and a dry shop does not stall it the same way. What humidity *does* to platinum is indirect — condensation on a cold master, wet clay dams, or a sweaty glove print that looks like inhibition. Do not switch a food cavity to tin because your hygrometer is high. Do not park a tin craft mold in a desiccant cabinet and then blame the brand when it stays tacky.

RUUIPON pours platinum as the default food path in Bao'an, Xinhe Blvd, Shajing, since 2018. Tin is a named craft choice when the dump and the master chemistry ask for it. Prototype is 3–7 business days after CAD lock. Production is MOQ 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies. Platinum shrink after a full cure is typically about 0.1–0.3%; tin continues to shrink in storage (cousin page, not this one). Steel/LSR *parts*: wydsilicone.com. Chemistry pick: platinum vs tin RTV.

Does not apply when the sticky face is SLA oligomer or latex poison on platinum, when you meant a food-contact chocolate well (we would not spec tin for that), or when the "humidity" is a wet dump — water in a plaster pour is not shop RH. LSR in a heated cavity with a cold-runner is a different plant.

Two cure systems, two moisture stories

Tin / condensation-cure. The polymer condenses, gives off a small molecule, and wants ambient moisture to keep going. Very low RH, a thick section with no air path, or a mold stored in a sealed bag while still green will stall. A 10:1 tin mix in a 20A–30A craft block can skin in a humid room and stay gummy in the core if you demold on a platinum clock.

Platinum / addition-cure. A/B 1:1 or 10:1. No moisture requirement in the same sense. High RH does not replace vacuum. Low RH does not replace a full cure. Platinum's enemies here are inhibitors and temperature, not the hygrometer.

Condensation on the master is neither of those cure stories. A cold CNC plate in a 80% RH room sweats. Water beads copy as pits or as a greasy film that can look like inhibition on platinum. Wipe and warm the master; do not raise tin content.

The photo that would prove the claim: hygrometer in frame with the flask, master surface dry under raking light, tin vs platinum kit labels readable. A foggy-window stock photo is not shop evidence.

flowchart TD
  A[Name the chemistry] --> B{Tin or platinum?}
  B -->|tin craft| C{RH in a usable band?}
  C -->|very dry / sealed tote| D[Open air path, do not bag green]
  C -->|ok| E[Mix 10:1 typical, pour]
  B -->|platinum| F[RH is not the catalyst]
  F --> G{Master sweating?}
  G -->|yes| H[Warm and dry the master]
  G -->|no| I[Weigh 1:1 or 10:1, vacuum, pour]
  D --> E

What a humid shop actually does to each dump

High RH on a tin bench can shorten working time. Mix smaller cups. Do not chase it by starving catalyst.

High RH on a platinum bench mainly risks wet masters, wet plaster jackets, and clay dams that off-gas. Platinum food wells still want a dry, sealed master and a vacuum collapse. We would not "help" platinum with a humidifier.

Low RH on tin stalls deep sections. Leave air to the back of a glove. Do not jacket a green tin skin in a sealed FRP shell the same hour.

Low RH on platinum is mostly a comfort number. Watch temperature instead — winter thickness is the other article.

ISO 3302-1 M2 remains a rubber drawing class. It is not an RH spec. CAD lock still freezes millimetres; it does not freeze a monsoon.

Failure: tacky tin in a dry tote

Symptom: tin craft mold stored in a zip bag with desiccant "to keep it nice" stays tacky on the face for days; edges that saw room air are better.

Cause: you starved the condensation cure of moisture, then sealed the starve in.

Confirm: a 20 g tin slug left open on the bench vs a twin slug in the same bag. If the open slug cures and the bagged one does not, you have an RH/air-path problem, not a bad lot number we will invent.

Fix: finish tin in open air per the grade, then bag. Recast if the face never recovered. Do not wipe "more catalyst" on a food-adjacent well — and do not use tin on food to begin with.

Platinum tacky-in-bag is usually incomplete cure or inhibitor, not missing moisture.

Typical shop values

Caption: typical shop values, not a named PO.

Humidity habits we would not recommend

We would not recommend tin for a chocolate or gummy cavity because "humidity is high so tin will cure."

We would not recommend bagging a green tin mold with desiccant.

We would not recommend a humidifier aimed at a platinum pour "to help it."

We would not recommend pouring platinum onto a sweating aluminum master.

We would not recommend reading RH as a substitute for vacuum.

Worked example: tin glove in a dry January studio

Prop mask, tin 10:1 glove, buyer in a heated 25% RH studio. Face stayed tacky at 24 hours; the lip that hung off the bench was closer to snap. They bagged it "to finish overnight." Worse the next morning. We recast the same sealed master in platinum 1:1 after they named the dump as PU, not food — different shrink band, vacuum, jacket. Prototype 3–7 business days after CAD lock. $50 CAD applied because the undercut map was not on the photos. Production MOQ 20 of that design. If they had insisted on tin, the fix would have been open-air finish, not a desiccant bag.

Mix-up: hygrometer as a chemistry switch

RH does not pick tin vs platinum. Dump chemistry, food vs craft, and inhibitor risk pick the chemistry. Humidity only tells you how a *chosen* tin will behave in that room. The other mix-up is treating condensation beads on a cold master as "the room is too wet for platinum" — dry the plate. Related: same mold for food and soap.

What to ask when you're buying

• Tin craft, or platinum food path — named on the RFQ, not implied by weather?
• Shop RH band if you will finish tin in your studio?
• Master stored cold enough to sweat when it enters the flask?
• Jacket on a green tin skin, or after snap?
• After lock, 3–7 business days, then MOQ 20 / design?

Related: contact, pour chemistry lock.

RFQ copy-pack — humidity vs chemistry

Paste into [email protected]:

Object: RTV mold, not an LSR/HCR part Chemistry: platinum food / tin craft named Dump material and peak °C Your shop RH if you finish the tool Master: will it sit cold then enter a humid room? Structure: open-back / split / glove + jacket 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 Who keeps the master

Send chemistry and whether the master sweats, not "humidity in my city." We pick tin only when you name craft — not a blank quote request. Phone +86 135 3006 2969. Xinhe Blvd, Shajing, Bao'an. Shop since 2018.

FAQ

Does humidity affect platinum silicone molds? Not as the catalyst. Wet masters and wet dams still hurt the face. Platinum 1:1 or 10:1 still wants vacuum and a full cure. RH is not a substitute.

Why did my tin-cure mold stay sticky in a sealed bag? Condensation-cure wanted moisture and air. Desiccant in a zip bag starves it. Finish open, then store.

Can I use tin for chocolate because my kitchen is humid? We would not. Food cavities stay platinum. Humidity is not a food-contact argument.

Will a monsoon shorten platinum pot life? Temperature and mix mass move pot life more than RH. Watch the cup, not the weather app.

Do you change the 3–7 day clock for a dry tin job? CAD lock includes a chemistry we can finish. A tin glove that must air-cure in your 20% RH studio is your finish, not our clock. MOQ 20 per design after the witness.