Smooth-Cast 300 vs 320 viscosity

[Luke0312]

I've looked over Smooth-On's site and the technical bulletin for each product, but didn't see a specific number.

I'm trying to find out how each of them compare in viscosity. The description for each one says low viscosity, however, Onyx also says the same thing and I've noticed a difference between it and 300, with Onyx being a bit thicker.

For those that have used both, can you notice a difference?

I'm planning on using Ure-Fil 3 to produce a terra cotta/baked clay feel, sound like a good idea? Know of a different additive to achieve the correct feel?

Does the 320 handle additives better than the 300? I might use the So-Strong Color Tint to also attempt to produce the correct color (terra cotta), but I question my ability to find the correct mix ratio of the colors. However, if I did, would the 320 be the best option for the color and ure-fil additives?

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I'll also email Smooth-On with these questions, but I wanted to get some answers from a variety of sources if possible.

 

[sgtfury4017]

I just used 320 on a project. It runs like water so be sure your mold, if in two parts, is properly bolted and possibly sealed along the edge with silicone calking. The so strong tint works really good. Very concentrated. Hope that tidbit helps.

 

[Luke0312]

I just used 320 on a project. It runs like water so be sure your mold, if in two parts, is properly bolted and possibly sealed along the edge with silicone calking. The so strong tint works really good. Very concentrated. Hope that tidbit helps.

So, as far as viscosity, is it the same as 300, at least to the eye?

As far as the mold, will probably use a jewelers cut on it. Clean-up will be simple, no intricate parts.

 

[robn1]

300 and 320 viscosity are both 80cps, Onyx is 100cps. 80 is about as low as it gets.

 

[bookface]

The 300 and 320 cure to slightly different colours, with the 300 being more of a bright white, 320 more of an off white/ivory. I've found the 320 to take pigments slightly better than the 300.

Urefil 3 doesn't really change the feel of a casting at all, and pigmenting the resin will remove any kind of visual difference that the urefil would make. The urefil 3 will make it much easier to slush, if it's a slush cast. If it's a straight pour, then the only real benefit you'll gain will be that it bulks up the resin and you'll use a little less.

 

[Luke0312]

300 and 320 viscosity are both 80cps, Onyx is 100cps. 80 is about as low as it gets.

Was that in the TB, did I just overlook it?

The 300 and 320 cure to slightly different colours, with the 300 being more of a bright white, 320 more of an off white/ivory. I've found the 320 to take pigments slightly better than the 300.

Urefil 3 doesn't really change the feel of a casting at all, and pigmenting the resin will remove any kind of visual difference that the urefil would make. The urefil 3 will make it much easier to slush, if it's a slush cast. If it's a straight pour, then the only real benefit you'll gain will be that it bulks up the resin and you'll use a little less.

Well crap, I misunderstood. Now that I reread the ure-fil description once you've mentioned it, I see that yes, it's just a look, not a feel.

Any ideas on an additive to give it more of a proper feel? I'm going to try some plaster in a batch to see how it turns out. I've also got some gypsum to grind and add, see what it does.

 

[robn1]

Was that in the TB, did I just overlook it?

Yes it's from the TB, listed as Mixed Viscosity.

 

[bookface]

To be honest, I've never experimented much with trying to gain a different feel to a casting, at least in terms of reproducing a stoneware piece, but I'd suggest your best bet would be something like ultracal or hydrocal, which are as close to a pourable stoneware that I can think of. Perhaps someone with more experience with either could suggest something. Maybe jesmonite? There are also jesmonite pigments that I know work with plaster, I'm sure they'd work with ultracal/hydrocal too.

 

[Luke0312]

To be honest, I've never experimented much with trying to gain a different feel to a casting, at least in terms of reproducing a stoneware piece, but I'd suggest your best bet would be something like ultracal or hydrocal, which are as close to a pourable stoneware that I can think of. Perhaps someone with more experience with either could suggest something. Maybe jesmonite? There are also jesmonite pigments that I know work with plaster, I'm sure they'd work with ultracal/hydrocal too.

Thanks, I'll do some test with the plaster and gypsum first with the 300, since I already have them on hand. Will report back on how it works so others will know. If it fails to give me the results I'm after I'll give the ultracal/hydrocal or jesmonite a try.

Trying to get it sorted so I can order the rubber and whichever casting material all at once.