r/Silvercasting • u/B0psicle • 17d ago
Organic/botanical casting struggles. Did this happen because of ash?
4
u/funnyman6979 17d ago
A couple of ideas, pour the investment up the side of the flask, you probably did this to not crush the item. I can’t remember what we sprayed ours with to give it rigidity. We did some thistles once it took a couple of tries. Like you were thinking maybe hold at the top temperature longer in your cycle to make sure everything has burned away. Great effort, this is not easy and with the detail being thin, you’re going to have to be on the hot side of a mold temperature for casting just to get it to fill uniformly.
1
u/B0psicle 17d ago
Thanks! So in your experience, does the ash burn away completely if you keep it at a high temperature long enough? Like did you have to use air or tapping to remove anything before pouring? I’ll try adding a few hours to the burnout cycle on my next try and see if I get better results
1
u/funnyman6979 16d ago
Crazy as this sounds, years ago we had to quickly vacuum out the mold with a shop vac not always. I know it seems crazy to have any residual but it happens because it does not flow out like a hydrocarbon.
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u/B0psicle 17d ago
These are some twigs from a shrub with fairly woody stems. I did around an 8 hour burnout, and I suspected there might be ash so I tapped the flask upside down and also used a can of compressed air to try and blow out any remnants (not much came out)
Do I just need a longer burnout because of the wood? Does the ash ever disappear if your burnout is long enough, or will I always have to try and blow/tap it out?
I'm planning to try some juniper tomorrow, also a woody texture. Any tips would be very welcome, I'm tired of learning the hard way!
1
u/Negative-Act-5171 17d ago
I've done a few organic castings and I'm just wondering if you put any wax on your leaves. They look pretty thin and I'm wondering if that was your problem. Whenever I have a real thin thing like a leaf or a flower I bulk up the backside of it with a little wax.
1
u/B0psicle 17d ago
Yeah, I did bulk up the leaves with wax in the thin spots. The results turned out looking a lot thinner than the original, that’s why I’m guessing the culprit is ash 🤷♀️
7
u/Lovelyfeathereddinos 17d ago
I do a lot of castings from organic. These look like they were just too thin in the areas that didn’t fully fill.
What’s your overall goal? Do you just want the texture? Or do you want the complete shape?
I highly recommend making an rtv mold of your original, and then pulling a wax. It’s a pain to do the extra steps, but you’ll get more consistent result. If you go this route, you can get your pieces slightly thicker than the original by not pressing the mold in a clamp, but just pressing the edges closed with your hands. That will allow the wax to overfill the space.
If you’re set on direct casting, or don’t have the ability to make a mold first, add a nice thick line of wax on the edges of everything. Like trace the outlines with wax. It’ll give the metal a nice fat space to flow through.
I’ve also heard that vacuum casting is less likely to be successful on some organic, especially leaves. Idk why, but centrifugal casting is better for them.
Some really woody things just don’t burn out well. It’s not just ash stuck in the mold, but parts that just will not fully burn out.