does silicone rubber float?

i am guessing yes, but does anyone know how well? or maybe im wrong?

As 1000kg [2,204.6 pounds] of pure water @ 4°C [39.2 F] = 1 cubic meter [35.3 Cu.Ft. ], those materials under 1000kg/cubic meter will float; more dense will sink, i.e. those materials with a specific gravity more than 1.

Specific gravity is the ratio of the density of a material to the density of water. The density of water is about 1 gram per cubic centimetre (g/cc). Materials which are lighter than water (specific gravity less than 1.0) will float. Most materials have specific gravities exceeding 1.0, which means they are heavier than water and so will sink.

Unfilled Silicone rubber has a SD of about 1.10 - 1.15; ergo, it will sink.

On a practical note; I have a 3" x 2" x 8" silicone rubber mold in my shop and it sinks like a rock.

That said, see:

United States Patent 6602102

Link to this Page: Buoyant silicone rubber compound - South, Valley Specialties

Abstract: A buoyant silicone rubber compound–and process for preparing same–is disclosed wherein hollow micro spheres are incorporated into the formulation in order to decrease the specific gravity of the compound to less than 1.0. The disclosed compound is prepared by admixing from about 85 to 99 weight percent polydimethyl siloxane with from about 1 to 15 weight percent hollow micro spheres. The micro spheres are selected to have a mean particle diameter of from about 10 to 500 microns. Aquatic gear comprised of the afore-mentioned buoyant silicone rubber exhibiting positive buoyancy/flotation such as ear plugs, swim goggles, dive masks, fins and sun glasses are also disclosed.

That was a spectacularly informative response. Would that we had more like it on this site.

G - O - O - G - L - E

either that or David Letterman’s “does it sink or float”.

thanks so much for the response, letterman was busy.

Most, if not all, silicones sink. From firsthand experience. They’re almost neutrally buoyant – a few pockets of air (10% by volume would almost certainly do it) will make it float.