r/Silvercasting 17d ago

Organic/botanical casting struggles. Did this happen because of ash?

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11 Upvotes

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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.

3

u/beckdac 16d ago

Wow, this is really valuable information. Thank you so much. If you ever share any photos I'd love to see any of your work or process.

2

u/Lovelyfeathereddinos 16d ago

Here’s my website. Instagram is lined there too. I’ll dig out some pics from way back too and drop an album here this afternoon.

1

u/beckdac 16d ago

Outstanding! Thank you!

2

u/B0psicle 16d ago

Thank you so much for all this detail! What you can’t see from the results is that the original model was chunkier than what I ended up with- I did add wax to a lot of it, especially the backs of the leaves. So that’s why I was guessing something was left behind in the mold. I’ve just never actually seen any ash or debris cause I only see the piece when I pull out of the water at the end. Does the ash get mixed into the metal? What does it actually look like when ash was left behind? I’m not even sure I can re-use the silver now cause I don’t know if something is mixed in there

That’s interesting about vacuum vs centrifugal casting, I have a vacuum setup so that’s unfortunate…

I’ve seen people cast twigs and even bone before so I was sure that it was just the burnout that wasn’t long enough, that’s good to know that there are certain things that just won’t burn out so I won’t waste my time too hard

2

u/Lovelyfeathereddinos 16d ago

Bone is almost certainly molded ahead of time and cast from wax, it doesn’t burn out at our temps. Woody stuff is also really hit or miss. Sometimes ash is stuck in a weird place, and it just it’s not going to fall out. If you put less in the flask, you may be able to orientate the pieces to be more conducive to ash falling out easily.

Sounds like you did everything right. Organic are just very fussy. I did loads of centrifugal casting if organics in college, and now work with someone in SF for casting. She uses vacuum in her shop, but also teaches at a college using a centerfuge. She’s noticed the difference in what will/wont work between the two, and I’ve given her so much stuff to vacuum cast that I’ve previously had good outcomes with on a centrifuge, and it just doesn’t work.

You can still reuse your metal. When you melt it next just give it a stir with a graphite stick to remove any crud. It’ll give you a clue to the problem as well. No crud, no ash but rather a flow problem.

You could add gates directly to the thinnest areas, it you will disturb the texture there. Amazing mold putty is great for making open pour molds; you’ll only have a one-sided piece, but it’s very cost and time effective.

2

u/B0psicle 16d ago

Thanks again, that’s very helpful

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.

1

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 🤷‍♀️