Casting Questions about casting, sanding, and pressure pots.

That pressure pot is a vacuum chamber and I know nothing about those, so I can't even tell you if it's a yes or a no.

I have used Oomoo, and I'd recommend you take one step up and use Mold Max, that way the molds will be a little more durable. Later on you'll want to look at platinum cured (addition cured) silicones. You can order online direct from SmoothOn and they also have distributors all over the US.

Why have you decided to use 325? The potlife is a bit short, I think?? The 325/326 resins are no good without pressure, as little bubbles form and are very visible. 305 is a great resin, less viscous than 325/6 and cures white rather than translucent straw yellow. Another one to look at is Task2/3 but those are more viscous again and require a lot of stirring before mixing the parts together.

You should always use a bit of primer, it helps you see the flaws in the surface (otherwise you don't see them till you pull out the resin cast) so that you can smooth them down more before molding. Acrylic auto primer/filler (no specific brand) comes in a spray can, you apply it, and then sand with 400-600-1000 or thereabouts depending on the quality of the surface grit wet or dry, then spray again. Sand and spray until you are satisfied with the surface. You'll want to use finer and finer grit paper and towards the end the sanding shouldn't take most of the primer off, just smooth and polish it.

Wet sanding you only want to do with sandpaper that is meant for it, and really only with the finer grits, nothing coarser than 240. So before that you should stick to dry-only sandpaper to get your surface smooth enough and take away lumps etc, then it's just a matter of working gradually finer to keep taking out the scratches. Primer really helps you see those.

For reproduction there is mainly Weiju (contact Ms. Lee at [email protected], or Grace at Jpopdolls) and Dollshe Craft. There may well be others but those two can be recommended safely, and are the only ones I know off the top of my head.

 

I have used OOMOO 30 silicone rubber and Smooth-Cast 300 and 305. The 300 doesn't have a long enough pot life for use in a pressure pot without being very rushed, while the 305 has a 7 minute pot life allowing me good results with my pressure pot. OOMOO 30 is a tin-cure silicone rubber and although makes a good beginner rubber to try out especially without a pressure pot, you may want to eventually use a platinum-cured rubber. I purchased the Dragon Skin 30 from Smooth-On, but have not tried it out yet so I can't say how well it works for doll mold making application. From what I know you can use the color tints with the 300 and 305 resins. I haven't tried it yet though, but I did buy the sample colors. I may have time to test it out this weekend with my 305 resin and will post my results in my WIP post about my Tiny Reindeer Doll. You can check that post for some pictures of molds and my blog as well for additional information on how my experience went.

I have been curious of the 325 resin, but not for doll application. I am also interested in making fish aquarium ornaments... but I would go with the 305 for doll making.

From the first message, what you posted a link to is a vacuum chamber. It works different from a pressure pot. I have never used a vacuum chamber, but just love the pressure pot I recently made. You can do a search to find more info on the forums. I did make a post about my making of the pressure pot not long ago as well.

 

You can definitely add pigment to 305. If you add pigment to 325 it will be like root beer, ie translucent, if you add pigment to 305 it will cure more pastel like, which is good for lighter fleshtones.

Oomoo and Moldmax are condensation cured/tine cured, they are cheaper an not as durable but also have less issues with cure inhibition, so good to start with. From what I've read the XLS is good, 25-30 is a good range of hardness, not too soft, not too hard. Tin cured silicone tends to give more shrinkage and you will probably need to post cure the mold after you remove the masters, to remove any alcohol residue that would negatively effect your resin castings.

 

Yes, definitely prime the wood. Wood is porous and you'll probably find that it takes several coats before it stops sucking up primer and starts creating an actual non-porous surface. You may also find that there's still a little bit of a texture of the wood grain, or some imperfections that were not obvious before priming, so you can get rid of those before casting.

I don't -think- you need to prime the resin in order to make a new mold from it, as resin is non-porous, but I'm of the "prime all the things!" mentality as I love how it suddenly shows you so many imperfections you may not have noticed otherwise.

 

Just to make sure, 305 needs a pressure pot but 325 dose not?

 

325 definitely needs a pressure pot and 305 does best with one as well.

 

I use the 325 series and yes it absolutely needs a pressure pot. If you are trying to get some interesting colors consistently, then going with that series is a good idea. it takes dyes really, really well. I would really recommend at the very least using 326 with a pressure pot -- I'm about to go to 327 personally, so I can cast a whole doll at once without having to rush. 7 minutes gets really short with 18 molds, haha. If you're going for strictly white resin or some simple light flesh tones, the 300 series is fine to use and works great in my opinion.

I second using mold max -- it's a much better product than oomoo, which tears very, very easily.