Plaster Mold: Bonsai Pot Casting

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Feet popped out of the mold in minutes.

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Feet popped out of the mold in minutes.

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Scored and slipped, the feet went ont.

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All finished up, the pot is now complete.

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Another view.

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I'm quite pleased with how the first pot came out.

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The copy and the original.
 
Here are some slight modifications I can apply to the pot. I chose this shape because I felt it was easy enough to make these slight changes. Should they be good, I would make another replication of it.
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Here are the pot comparisons after it had a chance to dry.
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The original pot is 1/4" bigger but after 8 hours, the replica pot shrank by that much.

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Here's a direct difference showing the shrinkage. I expect this to be 10-12% smaller. So in the grand scheme of things, it'll just be a tad smaller which is what I actually want since I have smaller-sized trees.

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Here's another pot pulled from the mold. The bottom is the first pot, the second is on top. It's currently in the queue to be fired. Super excited.
 
I got these back from the club president when I recently saw him. It just goes to show how much smaller these pots can get after firing.

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Side by side of the original pot vs the pot pulled from 1.0.

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Better size comparison. This makes me think that this is probably how the professionals shrink their pots so that there are size variations.

For the moment, I want to redo the mold for the original sakura blossom pot, given that now that I know the nuances. The next shapes I want to replicate next are moko pots.
 
All clays have a shrinkage rate when fired. If you want a 10-12% smaller pot make a mold of the pot that you pulled from the first mold and continue the process. Sooner or later you can get it down to mame size 😁

The only bad thing with molds is the storage space one needs to store them and the fact that they only last for so many pulls.
 
Pitoon said:
All clays have a shrinkage rate when fired. If you want a 10-12% smaller pot make a mold of the pot that you pulled from the first mold and continue the process. Sooner or later you can get it down to mame size 😁

The only bad thing with molds is the storage space one needs to store them and the fact that they only last for so many pulls.
Click to expand...
For sure, the storage space is going to be an issue if I made anymore molds. Do you have any pictures of your molds you can share?
 
That
lieuz said:
View attachment 415495
After the 8 hour mark, the clay was firm enough for me to add my chop mark and drainage holds.

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There is a support structure inside the pot that isn't shown. It's basically a sponge with a flat top and base.

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Drainage holes and wire holes were applied. Note the gap in between the mold and the clay. This was a clear indication the pot has more or less separated from the mold.

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Here is the pot removed from the mold with the support structure.

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The ridge that was removed from the original pot was put back in.

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The ridge that was removed from the original pot was put back in.

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This was the profile rib for the ridge/coil of clay that ran around the pot base.

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Cleaning up, I noticed there were some areas where the clay walls were off. This showed how the top warpage affected the opening.

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More finishing was done to the exterior walls. That coil added back into the pot was like going full circle.


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Top view. The pot is now ready for feet.
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That shit is tech. Nice work!
 
lieuz said:
For sure, the storage space is going to be an issue if I made anymore molds. Do you have any pictures of your molds you can share?
Click to expand...
My focus is on smaller pots, mame size. Here's one I just recently did and tossed out as the plaster was old. I just got a new bag of plaster so when I get some time this weekend I will start back up with the molds.

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lieuz said:
Wow you really got it all figured out. That form is clean as anything!
Click to expand...
I wish I didn't waste my time using that old plaster. I now have to basically start all over to make that mold. Doing a one piece mold is a lot faster that was what @ABCarve mentioned earlier in the thread.

lieuz said:
Looks like you got some root stand blocks going!
Click to expand...
I have a lot of projects going on......just need more time to finish them.
 
No picture update but the pots have been fired to bisque and no faults have been detected.

@Pitoon I use murphy's soap as a release agent. in your experience do you use any other that may possibly work better than the soap? I say this because the soap tends to gel up for some reason and it imprints those gel'ed up bits. The larger bits I'm able to remove, but the smaller ones also leave small imprints.
 
lieuz said:
No picture update but the pots have been fired to bisque and no faults have been detected.

@Pitoon I use murphy's soap as a release agent. in your experience do you use any other that may possibly work better than the soap? I say this because the soap tends to gel up for some reason and it imprints those gel'ed up bits. The larger bits I'm able to remove, but the smaller ones also leave small imprints.
Click to expand...
Murphy's Soap is technically a cleaning vegetable oil.

I use an actual mold soap from Laguna....... https://www.theceramicshop.com/product/2546/pure-lube-mold-soap-1-gallon/
 
Pots have been fully fired and of the two, one is glazed and the other isn't here are the final products.

Size comparison.
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Size comparison.
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Glazed comparison.
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Front
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Side
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Close up.
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Close up.
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Overview.
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