Optical Polish and Soft-Touch Surfaces on Beauty RTV

Optical polish is a master finish that the RTV copies, then the casting copies. Soft-touch is a hardness plus a micro-texture, not a coating you spray on the last dump. Beauty soaps, lipstick bullets, cream palettes, and applicator tools fail when one cavity is asked to be a lens and a rubber grip at the same time without a split in the spec.

This is about custom RTV molds for cosmetic packs you pour or press into: soap, lipstick, balm, powder palettes, mask sheets. LSR/HCR tools for mascara components and closures with a soft-touch pad are a different parts quote. The dirt that ruins a beauty cavity is the same species (oil, lint, haze), but the accept standard is a retail highlight, not a particle count.

Two surfaces, two measurements

Optical / high-gloss. The casting should read as a wet highlight under a point light. In master terms that is a high polish (SPI A-1 / A-2 class diamond polish on a metal master, or an equivalent named spec on a coated print). In RTV terms the rubber must copy that polish, then release the soap or lipstick without stretching the gloss into a matte smear. Any key witness, pour scar, or knit on that face is a reject.

Soft-touch. The finger should see a low-gloss, high-friction, slightly yielding face. That comes from Shore A of the *article* (often a mid-soft band for pads and puffs; the *mold* is often 10A–20A so it peels), a texture on the master (etch, laser, or EDM on metal; a specified print texture), and sometimes a geometry that flexes. A glossy 70A pad is not soft-touch. A matte 20A pad that tears in the cap assembly is not a product.

Write both Ra or SPI (or VDI for texture) and the rubber hardness on the face that needs them. “Make it look premium” is not a finish.

Masters that can hold a highlight

Cosmetic RTV likes a CNC or plated metal master so the polish does not chalk between color changes. Diamond polish in one direction, then a final wipe that does not leave a halo. Fill repairs in a mirror master will read as a witness unless they are re-polished through the same grit sequence; budget that, or recut.

Texture for soft-touch should be specified as a region or insert on the master, not as a blast that also hits the optical window. Mask. A common compact tool has a mirror lid-window region and a textured grip. Those are two master zones, two PMs, two accept lights — still one RTV skin if the split allows.

Venting analog: a key or overflow on a gloss face is a hairline that becomes a silver streak in the lipstick. Move keys to the texture, the back, or a well. The pour gate goes on a hidden lip.

Process that keeps the copy

RTV. Mix 1:1 or 10:1, vacuum degas until the foam collapses. Bubbles in a gloss face are rejects. Undercure at the surface makes a tacky gloss that fingerprints in the carton. Color in cosmetics is a batch-control problem; see the pigment article. For optical cavities, pour a dedicated natural or optical-grade platinum, not a cup that just ran carbon black.

Release. Beauty castings that will be overmolded, printed, or glued cannot wear a film of silicone oil. Barrier on the *master* if needed; no sacrificial spray in a food-adjacent or lip-contact cavity. A solvent spray on a puff tool will transfer into makeup and into the next adhesion test.

Demold. A stick-slip pull on a mirror pad puts ice-white stretch marks in the rubber. Those marks are not dirt. They are the polymer yielding. Use more draft on gloss faces than your texture faces, air assist, and a slower peel. Automated yank should not wipe the part across the polish.

HCR/LSR contrast. Compression tools pick up cloth texture from a dirty preform. LIM optical parts want a cold-runner and a dry cavity. Neither is this PO.

Soft-touch without turning the part into a lint magnet

Texture that is too aggressive holds powder, sebum, and carton fibers. Beauty returns then look “dirty out of the box.” Aim for a texture deep enough to kill gloss and raise friction, shallow enough to wipe. Specify a wear test: alcohol wipe, or the customer’s cleaner, and look for polish-through. Do not invent a cycle count in the brochure; run the customer’s method on a plaque.

Hardness: too soft and the pad mushrooms in the cap; too hard and “soft-touch” is only paint. If the article is an overmold on PP or ABS, that is usually LIM — different quote. On this site, keep the RTV skin even so a thick, soft region does not print jacket wrinkle.

Cleanliness is cosmetic, not optional

Lint on a mirror RTV pour is a black speck in a beige pack. Use lint-free handling and a cavity wipe protocol that does not leave fibers. Do not solvent-wipe a diamond-copied face with a paper towel. Powdered gloves leave prints. Bare hands leave sebum. Nitrile, changed, is the boring answer.

Common mix-up: one “high polish” for the whole tool

If the molder quotes a single polish for window and grip, they will polish the grip and texture the window, or the reverse, and both will be wrong. LSR steel inserts are the parts-tool version of the same split.

What to ask when you're buying

• Face A: SPI or Ra, no keys, no pour scar?
• Face B: texture code and article Shore?
• Master metal vs print, barrier coat, who keeps it?
• Platinum RTV, no cavity spray, food/lip-contact path if needed?
• First-article photos under raking light and a point highlight?

Worked example: lipstick bullet plus cap grip

Buyer wanted a high-gloss lipstick bullet, 12-cavity, platinum RTV, and a matte grip ring on the same pour. Split the master: A-side diamond polish, B-side specified texture, keys off the bullet face, 10A–20A skin, jacket so the row does not sag 0.5–1.5 mm. A sister PO for a 70A LSR pad on a compact was a parts quote.

When this article is the wrong quote

If you need LIM mascara components or optical LSR windows in steel, send the parts OEM. A tiny one-piece soap bar can skip a heavy jacket. Geometry can override: a locked filigree soap still wants a peel, not more polish.

Related reading: textures and logos in cavities, pigment bleed, release on the master, custom RTV molds.

Call this out on the beauty RFQ

Split the drawing views: Face A, SPI or Ra, no keys, no gates. Face B, texture code, Shore of skin vs article. Process platinum RTV. No sacrificial release in the cavity. First-article photos under raking light and under a point highlight, plus a wipe test if the part is a pad.

Send Face A/B callouts and the media (soap, lipstick, resin). We will polish the master, not the grip, and keep oil off the copy.

We would not recommend one polish spec for window and grip

We would not recommend solvent spray on a lip-contact cavity. We would not raise Shore A first to “get gloss.” We would not paste a LIM valve-gate vestige rule onto an RTV pour scar — hide the pour, don’t heat the runner. We would not weld-fill a mirror master “just to try.”

RUUIPON Mold Structure Decision: gloss lipstick is still a cavity you dump into. Flat back? open-back. Deep undercut filigree that cannot peel? two-part. Soft 10A–20A plus a wet pour? mother mold.

Typical shop values

Reference values only. Confirm material-specific limits against the supplier’s technical data and agree project acceptance criteria before production.

| Item | Typical shop value | | --- | --- | | Skin | Platinum 1:1 or 10:1, 10A–20A, vacuum degas | | Platinum shrink | About 0.1–0.3% after full cure | | Gloss master | SPI A-1/A-2 class or named equivalent | | Loaded-tray sag without jacket | About 0.5–1.5 mm | | Contrast: LSR *part* tool | Hot cavity, often cold-runner — different quote |

FAQ

Is soft-touch a coating you spray on the last RTV dump? No. It is hardness plus a specified micro-texture, sometimes a flexing geometry. A glossy 70A pad is not soft-touch. A matte 20A pad that tears in the cap is not a product. Optical gloss is a master finish the rubber copies; do not ask one cavity to be a lens and a grip without splitting the spec.

Why put the mirror window and the grip texture on two master zones? So PM, polish sequence, and accept lighting stay separate, and so blast or etch cannot hit the optical face. Fill in a mirror master reads as a witness unless you re-polish the full grit sequence. Keys and pour scars leave the gloss face.

Why more draft on a gloss face than on the textured grip? A stick-slip pull on a mirror pad puts ice-white stretch marks that are yield, not dirt. Air assist and a slower peel matter. A dirty master also prints cloth or layer lines into the copy.

Can solvent release go on a puff, lipstick, or soap tool? Beauty and lip-contact castings cannot wear silicone oil. Barrier on the master if needed; run the cavity without sacrificial spray. A solvent spray transfers into makeup and into the next adhesion test. Powdered gloves and paper towels on a diamond-copied face also print defects.

What should a beauty first article show besides dimensions? Split faces on the drawing: Face A with SPI or Ra, no keys, no pour scar; Face B with texture code and Shore. Photos under raking light and under a point highlight, plus a wipe test if the part is a pad. A single "high polish" quote will polish the grip and texture the window, or the reverse.