Silicone for a stroker sleeve: which grades and how soft

Short answer: no silicone you can buy off the shelf is certified safe against a body. Platinum cure silicone, sold as skin safe, is what home casters use, in the soft end of the range because reference sleeves run very soft, and the maker of the sleeve carries the risk. Everything below explains why that sentence is worded the way it is.

This page is not medical advice. It reports what the manufacturers, the standards and the health sources say, and where they stop. For adults (18+).

• Platinum cure only
• What the labels certify
• "Medical grade" and "body safe"
• How soft: shore for a sleeve
• Dual density
• Pigments, additives, release agent
• Where to buy (EU)
• Picking one
• Sources

Platinum cure only

Two-part casting silicones are named after the metal that starts the cure. Tin cure costs less, but it is never body-safe for this use: use platinum cure only. Platinum shrinks less and keeps its shape for decades. [Smooth-On FAQ 184] It needs no post-bake to drive off cure by-products, so it leaves fewer extractables behind, and the medical grades in that family are the ones that meet food-contact and biocompatibility tests. [SSP]

Platinum has one awkward habit: it refuses to cure against the wrong surface. Sulfur, amines and amides, tin salts, phosphorus compounds and some primers all stop it, leaving the surface sticky. [Dow] [FAQ 104] Tin cure and platinum cure will not cure against each other either. That is why the prepare step asks for a test patch in a corner of the mould before you pour the whole thing, and why printing covers what on a print can stop the cure.

What the labels certify

Four labels turn up on silicone sold to hobbyists. None of them says "safe inside a body". Here is what each one actually covers.

• Skin safe. A manufacturer's category, tested by an independent lab for contact with skin. Smooth-On applies it to cured Ecoflex 00-30 and Dragon Skin 10, gives no warranty with it, and leaves suitability to you. [FAQ 205] No page we read extends it to mucous membranes.
• Food contact, 21 CFR 177.2600. A US rule for rubber articles in repeated contact with food. It lists the polymers and sets extraction limits for aqueous and fatty foods. [Cornell LII] It is a food rule, not a body rule, and Smooth-On says plainly that complying with it is not FDA approval. [FAQ 126]
• USP Class VI. Three animal tests on the material: systemic injection, intracutaneous, implantation. Pass or fail, on the material alone. It does not judge a finished device and does not replace approval. [Elastostar]
• ISO 10993. The one that does look at a finished device, under its real conditions of use, risk by risk. [Elastostar] A home cast has never been through it.

The European counterpart to the food rule, LFGB, cannot be self-certified and adds sensory testing, where FDA food-contact compliance can be self-attested. That comes from a retailer page, so treat it as a pointer rather than a citation. [Greenvyne, retailer]

"Medical grade" and "body safe"

Neither phrase has a legal definition in the sex-toy trade. A toy maker saying "body safe" is telling you what they believe, not what a body has tested; the trade runs on trust, and the honest move is to ask for third-party test reports. [Dame] Sex toys largely escape regulation and are still sold "for novelty use only" in places. [Public Health Post] Health writing that does name materials puts medical-grade silicone, borosilicate glass and stainless steel on the usable list, and warns that porous rubber and vinyl hold bacteria. [WebMD, medically reviewed]

So a home-cast sleeve in skin-safe platinum silicone is not a certified body-safe toy. It is a home cast in skin-safe platinum silicone. That is the whole claim, and it is the reason this site never makes a bigger one.

How soft: shore for a sleeve

Hardness is measured on scales that run 00 (softest), then A, then D. They overlap: 95A is roughly 45D. [Smooth-On] Reference sleeves on the market run very soft, so a canal is usually cast much softer than the shore 10 to 30 A that suits a firmer shape: 00-10 to 00-30 is the typical range here.

Shore, pot life and demould time from the product pages. [00-10] [00-30] [DS 10] All mix 1A:1B by weight or volume, with a density around 1.07 g/mL. Verify every figure against the current Smooth-On technical data sheet before you buy or pour: a product is revised over time, and figures copied out of date are worse than none.

All of them are 00-10 to 00-30, too soft to hold their own shape reliably at the entry and the flange: 00-10 in particular tears easily right where a sleeve gets handled most. Slacker, mixed in at 1 to 3 parts, softens a base further and adds tack; check which base it's approved for before you use it. [FAQ 138] A rule of thumb, not a citation: for a cast you pull out of a mould, 70A is already too stiff, and 30A and below bends out of detail without tearing.

The author's own taste: shore 10 to 20 is soft and pleasant for the canal, and 30 is as firm as they'd go for a single-density pour. That is one person's view, not a tested figure.

Dual density

The idea, not yet built or tested at full scale in this tool: cast the sleeve in two layers, a harder silicone (Dragon Skin FX-Pro or Dragon Skin 10) round the outside for the entry and the flange, and a softer one (Ecoflex 00-20 or 00-30, optionally with Slacker) for the canal itself. The outer layer carries the flange and the grip through the walls of the machine or the hand; the soft layer gives the feel.

Order and bonding matter. Pour the hard layer first, round a core sized to the canal plus the soft layer's thickness, and let it cure fully. Then swap in the core that carries the full canal shape, without any release agent on it this time, and pour the soft layer into the gap within about 24 hours of the first cure. Platinum silicone only bonds to cured platinum silicone when the surface is clean: no release agent, no soap residue, no latex-glove contact on the surface it has to bond to. A release agent used at this stage stops the bond rather than helping it. Test the bond on a scrap piece before you commit a full sleeve to it.

Pigments, additives, release agent

Whatever a silicone was tested as, you change it when you add to it. Colour pigments need their own testing and are not covered by the base material's certificates. [SSP] The same goes for thinners, accelerators and any release agent left on the surface of the cast. A rinse and a full wash before first use is the minimum, and it is in the clean and store step.

Where to buy (EU)

Smooth-On ships from the US, and shipping platinum silicone across the Atlantic costs more than the silicone. Three EU suppliers with platinum-cure ranges and published datasheets: FormX, Silikonfabrik and MB Fibreglass (which carries Polycraft PlatSil and Silskin). Read the datasheet on the supplier's own site before buying; grades and names differ from the Smooth-On ones named above, and the table above is a starting point for what to look for, not a shopping list of exact products.

Picking one

A working default, not a recommendation: a platinum cure silicone sold as skin safe, in the 00-10 A to 00-30 A range for the canal, bought fresh from a supplier who publishes datasheets. Read the datasheet for the mix ratio, the pot life and the cure time before you open anything, because the pot life starts the moment the two parts meet.

Then the practical side: the casting guide walks the whole process, from printing the mould and the core to the first wash. The designer works out how much silicone your sleeve needs, in millilitres, while you draw it, and the figure already includes the waste allowance: no need to add your own margin on top of it. The gallery shows what other people have drawn.

Sources

Read on 2026-09-20. Pages change; check the current datasheet. Manufacturer pages: Smooth-On, Dow, SSP. Standards: Cornell LII for 21 CFR 177.2600, Elastostar for USP Class VI and ISO 10993. Health: WebMD (medically reviewed), Public Health Post. Trade: Dame. Retailer pages are marked as such in the text. The full list, with what each page says and where sources disagree, is in docs/GUIDE-SOURCES.md in the project.