califire Posted June 9 Report Share Posted June 9 Hi, I was going for a 2 part mold and didn't consider the nodules creating minor undercuts. I successfully poured the first half of the mold, using Murphy's soap as a release agent. My box released just fine. However as I began work on cleaning up the mold, I began noticing that the nodules are pretty pronounced and it had me worried that it might be locked. So while it's still curing, it's been 18 hours or so since I poured it and it's cool to the touch, just a little damp. I decided to see if I could release it. And sure enough the mold began to crack where a nodule is pronounced. Is it impossible to create a mold of this object? Should I have gone with silicone instead of plaster? 😔 https://drive.google.com/drive/folders/1BcaNTbOXf3EdxWTAENu3z4K2JL2BTQB0 this is the ammonite before my attempt at creating a mold. https://drive.google.com/drive/folders/1_A0XuSmRJLD5xphqZnv372sUsFgOQ5uY this is the Ammonite casting process. I was thinking that I could maybe cut the mold in half and run a dowel through it to keep it consistent. Maybe it's not too late and I can pivot to a silicone mold here and pour the half with silicone, and then break off the other plaster portion and pour the other half as silicone? Any advice would be appreciated. This my first time doing this Quote Link to comment Share on other sites More sharing options...
califire Posted June 9 Author Report Share Posted June 9 update it's released from the plaster but it's locked in the mold 😭 I can turn it completely upside down and it doesn't come out but sort of moves around in the mold 🤔 Quote Link to comment Share on other sites More sharing options...
califire Posted June 10 Author Report Share Posted June 10 Okay so im going to continue with the second half but I've built up the nodules to be convexs vs concaves so that it won't lock when released. Then I'll gently break the other half rebuild those nodules and repeat. It won't be an exact replica but when pouring the second mold I can build out the convexed with clay and then the casting will release because the nodules won't lock and instead they'll slip out because of the clay. Quote Link to comment Share on other sites More sharing options...
califire Posted June 11 Author Report Share Posted June 11 https://drive.google.com/file/d/1aw3F9yLnhoupMOMob-RVeY6IxarAWLt3/view?usp=drivesdk Okay so using convexed and not concaves worked for one side! Gonna bust the second one out now! Omg this makes me happy Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted June 11 Report Share Posted June 11 Hello Califire, I'm not familiar with an "ammonite". What material is it made of? (Is it a shell or is it stone?) Murphy's only really works on porous surfaces, is the molded object porous? If I had been presented with this, I would have gone in the direction of a rubber mold, to get a plaster duplicate, and then start the molding process with the plaster duplicate. Whenever I cast something and it locks up the first pouring, I usually gently break the first casting and then add clay, as you describe, and then repour. Now that you know the piece is complex you might consider making it more than just a two piece mold. Also, that looks like a heavy mold, you might get yourself a tree saw and cut the corners off to lighten it up, (Tree saws are great for plaster.) Good luck Hulk 1 Quote Link to comment Share on other sites More sharing options...
califire Posted June 11 Author Report Share Posted June 11 (edited) And she's free! 😁 https://drive.google.com/file/d/1awHbPs5_owhpVVPQ8ZKiADaIlS9BizHn/view?usp=drivesdk https://drive.google.com/file/d/1azca0FvcJjKLasrsjR6v5HQE_ajUN5Sa/view?usp=drivesdk @Jeff Longtin thanks for the reply! The Ammonite is a super hard stone. I was considering rubber/silicone but was super nervous about the process. Looking back it probably would have been better. I was definitely considering more than two parts, perhaps breaking it up in four hemispheres for each side. It seems I wasnt too far off the beaten path. I might even still cast this to silicone for a mother mold once I managed to squeak out a working plaster mold. I'm just glad I'm getting the ratios right, both pours were spot on the money with the mixture and solid. This second pour came out like pancake mix, it laid down smoothly. It's a shame I had to break the other mold but I'm so thrilled to have my expensive piece back lol. It's very easy to see where it locked at. Even though the Murphy oil wasn't absorbed by the Ammonite very well, it released nicely from the plaster when encouraged to do so. I'll give this another to when I get some more material from my supplier. Ps thanks for the recommendation about the tree saw, it's definitely a heavy mold lol 😞 Edited June 11 by califire typos Hulk 1 Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted June 11 Report Share Posted June 11 That looks great. Congrats! A few other suggestions: I notice that your "keys" are small little bumps. With such a large mold its super easy to wear down small keys. (Unless you're very strong, gently positioning a heavy mold, is very difficult.) Once you start wearing down the keys it's difficult to align the mold parts. Instead think about making larger keys. (Mostly width wise.) Also, there's no reason a key needs to be a little round bump, in many factory photos I've seen keys that are raised shapes that simply accommodate the shape of the molded piece. (Think, for instance, the rings around Saturn.) If your keys were a raised ring form, around your round model, it would be super easy to set the top mold onto the bottom mold when you assemble them. califire 1 Quote Link to comment Share on other sites More sharing options...
califire Posted June 11 Author Report Share Posted June 11 (edited) 21 minutes ago, Jeff Longtin said: That looks great. Congrats! A few other suggestions: I notice that your "keys" are small little bumps. With such a large mold its super easy to wear down small keys. (Unless you're very strong, gently positioning a heavy mold, is very difficult.) Once you start wearing down the keys it's difficult to align the mold parts. Instead think about making larger keys. (Mostly width wise.) Also, there's no reason a key needs to be a little round bump, in many factory photos I've seen keys that are raised shapes that simply accommodate the shape of the molded piece. (Think, for instance, the rings around Saturn.) If your keys were a raised ring form, around your round model, it would be super easy to set the top mold onto the bottom mold when you assemble them. Thank you, thank you, it's a sweet relief I didn't ruin the fossil lol 😅 I slept so well last night after freeing it 😁 Interesting 🤔 so I could put some clay around the shape of the mold to create that lip you're suggesting? That's brilliant! I was looking at them this morning sulking a little because I just knew that one or two castings and I'll wear them down because they're so tiny haha. Thanks for the suggestion, I'll add a positive ridge around the shape before my next pour! 🙏 Edited June 11 by califire Quote Link to comment Share on other sites More sharing options...
califire Posted June 14 Author Report Share Posted June 14 I did it! https://drive.google.com/file/d/1cG5_NVN57ybdIgECRoWztg_bdw9MBpfd/view?usp=drivesdk woohoo 🙌 🎉, what a journey and learning experience it has been lol. Not bad for my first time making a mold ever, not to mention using plaster. Every bit of this process was me learning how to do the thing Chilly and Hulk 2 Quote Link to comment Share on other sites More sharing options...
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