How Long to Vacuum-Degas RTV: Foam Collapse | RUUIPON

Vacuum time on platinum RTV is a visual end point, not a two-minute internet spec. You pull the chamber until the mix rises into a foam and then collapses, and you hold a short extra so the last bubbles at the cup wall pop. If the foam never falls, you have too little headspace, too much whipped air, a cup that is too full, or a mix already climbing pot life. Clock bands in a shop are typical — often a few minutes to around ten on a small cup, longer on a large mass — and they change with viscosity, temperature, and how hard you mixed. We would not ship a food-contact logo cavity from a cup that never collapsed.

RUUIPON vacuum-degases platinum A/B in Bao'an since 2018. 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. Degassing *epoxy* for jewelry is a different viscosity and a different pot; jewelry is not food. LSR *parts* in a heated steel cavity with a cold-runner: wydsilicone.com. Service: vacuum-degassed platinum trays.

Does not apply when the craters are inhibition (sticky face, cured back), when you are pressure-potting *resin* in a finished mold, or when a hobby video says to skip vacuum and "just pour from height." We still vacuum food logos, thick gloves, and transparent resin tools. A cousin page covers when we refuse to skip the chamber entirely.

Collapse is the spec; the clock is a shop band

Pull. The mix should climb. If it barely moves, the pump is weak, the gasket leaks, or the grade is already thick from a cold room or a late mix. If it explodes over the rim, you overfilled the cup — that overflow is wasted rubber and a starved box, not a longer cycle.

When the dome falls and the surface looks like broken foam rather than mousse, you are close. Hold a bit so wall bubbles walk out. Then break vacuum slowly so you do not re-whip the surface. Pour in a thin stream onto a brushed detail coat. Vacuum does not wet a serif; the brush coat does.

If foam never collapses inside pot life, stop. Dumping a still-foaming cup into the box traps a crater field against the master. Remake the mix. A second vacuum on already-gelling rubber just lifts a skin and sets wrinkles.

Typical shop bands (not a named lot, not a lab timer): small cups often collapse in a few minutes; larger block mixes can sit toward the long end of a 5–15 minute window depending on viscosity. Warm, low-viscosity platinum is faster. A 10A high-tear grade can hold foam longer. Write "until collapse + short hold" on the SOP, not "2 minutes because a kit said so."

The photo that would prove a degas is the cup at full foam, the same cup after collapse, and a raking-light cavity with no pinholes. A timer screenshot is not that photo.

Typical shop values

Caption: Typical shop values.

Common mix-up: two minutes is a vacuum specification

Buyers copy "degas 2 minutes" from a kit and then argue the cavity pinholes are "normal." Two minutes is sometimes enough for a warm, thin, well-folded cup and often not enough for a whipped 10A mass. The cousin mix-up is vacuuming *after* the pour in an unsealed box and calling that degas — you will suck air *into* leaks. Vacuum the cup, then pour. Pressure on the closed box is a different machine (see the pressure-pot vs vacuum page when you file that RFQ).

Worked example (anonymized)

A 900 g 1:1 platinum for a 12-cavity resin plaque. First cup was whisked, filled to the brim, pulled for a flat two minutes. Foam hit the lid, never fully fell, pour showed a dust of pinholes on every logo. Remake: same grams, spatula mix, 30% headspace, pull until collapse plus a short hold (that run sat nearer the long end of a small-cup band because the room was cool), brush coat, pour. CAD was already locked — no extra $50 — second proto skin still inside the 3–7 business day window. Production MOQ 20 used the same SOP. Food was not on this plaque.

We would not recommend

We would not recommend a fixed two-minute vacuum as a PO spec.

We would not recommend filling the cup to the lid "to match the calculator grams."

We would not recommend skipping vacuum on a food-contact logo because the clock felt long.

We would not recommend a second pull on a mix that has started to gel.

flowchart TD
  A[Mixed A/B in a cup with headspace] --> B[Pull vacuum]
  B --> C{Foam rises then falls?}
  C -->|yes| D[Short hold, slow break, pour]
  C -->|overflow / never falls| E[Stop — remake, more headspace, less whip]
  C -->|barely moves| F[Check pump, gasket, mix temperature]
  D --> G[Brush coat on master still required]

What to ask when you're buying vacuumed skins

• Is the shop SOP "until collapse" or a copied kit timer?
• Do food cavities and clear resin tools always see the chamber?
• What happens if foam has not fallen and pot life is ending — remake or pour anyway?
• Who sizes cup headspace against the grams you quoted?
• After CAD lock, 3–7 business days then MOQ 20?

Related: RTV molding, quote.

RFQ copy-pack — degas as a line, not a minute count

Email [email protected]:

Duty: food logo / clear resin / figurine / concrete (not food) Mix: platinum 1:1 or 10:1 Vacuum: until foam collapses + short hold — required Do not skip chamber on this face CAD: locked / USD $50 if you model Prototype 3–7 business days after CAD lock, then MOQ 20 / design

Send the duty and the grams. We degas to collapse, we do not sell a two-minute checkbox. Phone +86 135 3006 2969. Desk: contact.

FAQ

How many minutes should I vacuum RTV? Until the foam collapses and you hold a short extra, while you are still inside pot life. Typical small cups are often a few minutes; larger masses can run longer. Write the visual end point on the SOP.

What if the foam hits the lid? You overfilled or over-whipped. That cycle is not a degas. Remake with headspace. Overflowed rubber is not "extra vacuum."

Can I vacuum the mold box instead of the cup? A sealed chamber around a closed box is a different setup and can pull air *in* through leaks. Our default is cup degas, then pour. Ask before you invent a box-vacuum SOP on a food tray.

Does a longer vacuum make the rubber stronger? No. Past collapse you are only burning pot life. Tear strength is the grade and the geometry, not an extra ten minutes at 29 inHg.

If pinholes remain after a full collapse, is that still a vacuum miss? Sometimes a missed brush coat, a pour from too low, or inhibition craters. Confirm with raking light and a cut sprue before you "degas longer" on the next cup.

When collapse still leaves a dusty face

A cup that collapsed cleanly can still pour a pinhole face if you drop the stream onto a dry vertical logo, skip the detail coat, or break vacuum so fast the surface re-whips. Confirm location before you add minutes to the next cycle. Open craters cloned in every dump are a mold-face problem: remake with coat + collapse. Pinholes only in *your* resin, with a glossy empty well, are a casting problem — pressure pot the dump, do not "degas the RTV longer."

ISO 3302-1 M2 on the drawing will not vacuum the cup for you. Neither will a tooling charge. If the proto skin fails raking light, we remake the pour inside the same CAD lock when the miss was shop mix/degas. A logo change is a new face.

Jewelry UV resin and concrete dumps do not inherit a food extraction pack just because the rubber saw a chamber. Vacuum is process quality. 21 CFR 177.2600 is a different document.

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