SAM-32 Silicone Adhesive / Silpoxy 3-ounce tube
One part silicone adhesive & paint base
People are asking about how 1-part silicones fit into the range of materials available to silicone artists. Here are Tom McLaughlin's views on working with 1-part silicone:
USING 1-PART SILICONE by Tom McLaughlin (c) 2022 Silicone Art Materials
1-part silicones are the most popular silicone in the world!
Silicone caulking seals and waterproofs bathtubs and sinks on every continent.
1-parts are formulated as adhesives.
They are far more adhesive than 2-part (A/B) silicones.
No need to measure different parts.
1-parts set up as they meet the air, from the outside to the inside.
1-parts are Condensation Cure silicone and need moisture and air to cure.
That’s why they don’t set up in an airtight tube.
Formulated with just the right amount of curing agents, 1-parts set up every time.
Replace cap on tube as soon as possible.
Improperly closed caps will cause 1-part silicones to set up in the tube.
To help prevent cap from sticking, wipe a little petroleum jelly or mold release on the threads.
Platinum silicones will not set up on top of 1-part silicones.
1-parts all contain Tin, a Platinum silicone No-No.
When a platinum silicone pour just won’t take platinum silicone paint no matter what you try, using a 1-part silicone as a paint base may be the only option to complete a project.
SAM-32 / Silpoxy
The new high strength, fast set 1-part silicones have exotic cross-linkers. They are stronger, cure faster and stick better to a wider range of materials than ordinary silicone caulking. This is why they are so popular with silicone doll and special effects people.
AS AN ADHESIVE
1-part silicones come as a thick paste - like toothpaste.
It’s best for gluing repairs at this consistency.
Very little is needed to repair torn silicone.
A toothpick may be the best applicator for most repairs.
Wipe off excess with a sponge or paper towel moistened with isopropyl alcohol.
The trick is setting a glued piece down undisturbed while the adhesive cures.
Heat from a hair drier and a spray of water will help speed cure time.
Regular silicone caulking from the hardware store fully cures overnight.
SAM-32 and Silpoxy cure in minutes with applied heat.
TEXTURING
As a paste, 1-parts can be used for texture. Patting with a brush or sponge will give interesting texture effects. Apply matting powder over a layer of 1-part, and textures can be stamped into the surface with coarse sandpaper, sponges, brushes, etc. Once cured, excess matting powder can be rinsed off with water or solvent.
AS A SILICONE PAINT BASE
For use as a paint base, 1-parts need to be thinned with a solvent.
This is purely a by ‘feel’ thing.
50/50, equal parts solvent and silicone by eye is a good start.
Always add pigment to silicone first to get the ratio right, then add solvent to thin.
1part silicones are firmer than pouring silicones.
Usually between Shore A 20 and Shore A 40 Durometer.
Paint layers want to be thin to prevent a firm skin from forming.
HIGHLY ADHESIVE = HOLDS MORE PIGMENT
Since 1-part silicones are so very adhesive, they can take higher pigment loadings than A/B silicones. This ability to load 1-parts with pigment makes them great for painting hair and intensely colored details. Try 1 part pigment to 2 or 3 parts high strength adhesives like SAM-32 or Silpoxy by volume. For general painting, try working with more pigment than you usually do with A/B silicone and thin with solvent for delicate toning and washes.
AS A SEALING COAT
A thin layer of 1-part silicone on top of a paint job done with a softer 2-part like Psycho Paint will give protection from abrasion. This is not unlike human skin, which has a horny firm layer on top of softer tissue. The trick is you don’t need much. Thin 1-part silicone with 2 or 3 parts solvent by eye before applying a thin, even coat with a brush or sponge as a sealer. Think of it as a soft version of varnish used to protect wood. If you want to do this with Platinum silicone, there are a number of firmer translucent silicones you can use, like Dragon Skin 10, 20 or 40 (higher numbers mean firmer).
AS A BONDING COAT FOR MATTING POWDER
High strength 1-part silicone adhesives bond matting powder better than anything else.
You need to work fast as you only have about 5 minutes of working time.
The most common mistake with “wet” matting is using too much silicone for the bonding coat.
This can result in crusty clumps of matting powder and a thick finish.
Very little silicone is needed to permanently bond matting powder.
It’s recommended to thin silicone with a solvent in equal parts (50/50).
Smooth-On Novocs is fastest, SAM OSS, naphtha, Bob Ross thinner etc dry slower.
Apply liberally with a 1-inch chip brush, getting it into every crack and crevice.
With a fresh brush go over entire surface removing as much wet silicone as possible.
Wipe brush on paper towel to clean it if necessary.
With a latex-free sponge STIPPLE, pat lightly over the entire surface, removing any remaining excess, paying particular attention to removing any puddles from creases and evening out the silicone all over.
Pour matting powder in a cup and load a fresh 1” chip brush or powder brush from that. Load brush with powder and apply to the wet silicone, barely touching the surface.
Avoid getting silicone on the brush as much as possible.
Keep brush full of powder and continue until the surface is fully covered in powder.
Lightly tap - pounce - the brush on the powder to force the powder into intimate contact with the wet silicone.
Allow to sit undisturbed until cured.
With fast set 1-part silicones this could be 1 hour.
Clean brushes in solvent for reuse.
Once cured, remove excess powder in a water bath with detergent or baby shampoo.
Rinse in clean water, let dry.
Alternately, excess can be removed with a sponge or paper towel moistened with water.
LONGEVITY
There is a concern if materials like 1-part silicones are ‘archival’. Archival means to last for a long time. With art this usually means how long a pigment will retain its color without fading, or a paper staying white and not yellowing. With rubbers it refers to how long a rubber will retain its physical properties. In the case of collectors’ silicone dolls, how long they will last with moderate light use.
2 part (A/B) Tin cure silicone has a bad reputation for breaking down, especially when silicone fluid is added to make it softer. And it does. Molds made from 2-part Tin cure silicones have a useable life of 5 years or so. Although 1-part silicones use Tin to cure them to a rubber, the chemistry is very different to 2-part Tin cure silicones. 1-parts can last very long indeed. How many times during a lifetime does a bathtub need to be re-caulked with silicone caulking?
Animatronic silicone figures in theme parks are usually painted with contractor’s caulking from a paint store. These animated figures go through hundreds of thousands of motions in their lifetime and are usually made of Shore A 10 to 30 Durometer silicone. Silicone medical prosthetics and appliances are generally made of firmer/stronger silicones in the Shore A 30 to 50 Durometer range for durability. In both applications - daily prosthetic wear and constant animatronic flexing - the author’s experience is theme park contracts and medical insurance will try to get 7 years use out of a silicone piece before replacement. But the reality is closer to 5 years being the limit for repeated, daily use.
As the reborn silicone doll world is relatively new, we don’t have any definitive long-term data. But it’s not like one day you’ll open your display case and a silicone doll will crumble to pieces. Silicone has a much longer life than natural latex, which turns yellow then brown and gooey when exposed to sunlight and the atmosphere. 7 - 15 years is about the limit for anything made from natural latex rubber. Silicone will yellow slightly in time, but holds onto its mechanical properties much longer than latex and many other rubbers. 25 years can be easily expected from silicone rubber as a collector’s piece. Maybe 50 years or more. A lot has to do with how soft a silicone is and how much it is handled. Firmer silicones are stronger. Soft “marshmallow” silicone frequently handled and dressed will “chafe” on the surface. (This is where a protective coat of a firmer silicone can help extend the life of a doll.) Properly cared for, a well-made Platinum silicone doll could be expected to be left to your grandchildren.
