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#41 Mark C.

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Posted 28 June 2013 - 06:59 PM

Vaseline at least for me is not something I would have used.
As far as the bubbles NEXT time vibrate the mold more right after pouring and they should go away. The broken pieces are from sticking so better release measures next time.
Go to a drug store and buy some green soap for release agent and use the vasiline for something else.
Looks like a good 1st try.
Mark
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#42 Biglou13

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Posted 28 June 2013 - 07:34 PM

Interestingly enough the top of the mold was cool but once I opened it up the inside was still hot. There is some damage on the top of the mold and some air bubbles at the bottom. The sides are okay but are a little greasy from the vaseline. I'm not too concerned about the damage at the top but the bubbles at the bottom bother me. Is there any way to fill them in and smooth off the bottom?

Once again thanks so much to everyone for your help! I can't believe my first mold might actually be usable!

Evan


The bubbles on bottom would bother me also. I don't know how technically smooth you need it. But maybe you can fill holes with more plaster . Smooth as much as possible with straight spatula, dry , Sand it smooth. ( it works on dry wall). Guess I've gotten lucky with few I've made.

I'm also wondering If you could place master in mold and re pour rim?

How are you going to use mold?

I use Murphy 's soap for release agent, no problems ....yet.
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#43 Strelnikov

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Posted 28 June 2013 - 07:36 PM

Thanks Mark the credit goes to you and everyone else who helped me out.

Will do the steps to get rid of the bubbles next time, I read your post about this after I had already poured the mold and the top had hardened.

What brand of green soap should I use?

Evan

#44 Strelnikov

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Posted 28 June 2013 - 07:55 PM

The bubbles on bottom would bother me also. I don't know how technically smooth you need it. But maybe you can fill holes with more plaster . Smooth as much as possible with straight spatula, dry , Sand it smooth. ( it works on dry wall). Guess I've gotten lucky with few I've made.

I'm also wondering If you could place master in mold and re pour rim?

How are you going to use mold?

I use Murphy 's soap for release agent, no problems ....yet.


I could try sanding the bottom to get rid of the bubble holes. Either that or next time I pour a mold I could pour a bit in the bottom to cover the holes (if that would work).

I don't think the damage at the rim is going to be a problem. I just won't be able to pour slip all the way up to the rim.

This mold was mostly a practice mold although I will at least try it to see how it works. My wife (the potter in the family) wants me to make a beer stein mold that will have to be a two-part mold. Before I tackle something that complicated I wanted to make sure I could confidently make simple one piece molds.

I would have tried the Murphy's soap but it didn't cover up the mistakes in my woodworking skills (not my day job) and the Murphy's soap really bubbled a lot. Because of that I went with something thicker like vaseline.

Evan

#45 Biglou13

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Posted 28 June 2013 - 08:43 PM

With Murphy's soap I don't use a brush, I use a small piece old t shirt.

I started with brush to many bubbles, then wiped bubbles with t shirt rag.... Now I just use small square of t shirt.

If any small bubbles I wipe off with moist oils soap rag.
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#46 Strelnikov

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Posted 28 June 2013 - 08:50 PM

With Murphy's soap I don't use a brush, I use a small piece old t shirt.

I started with brush to many bubbles, then wiped bubbles with t shirt rag.... Now I just use small square of t shirt.

If any small bubbles I wipe off with moist oils soap rag.


Okay thanks for the tip.

Evan

#47 OffCenter

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Posted 28 June 2013 - 09:10 PM

Avoiding air bubbles will probably be a bigger problem than any of your present concerns.

Jim


Damn! I was right again.

Jim
E pur si muove.

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#48 Strelnikov

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Posted 28 June 2013 - 10:16 PM


Avoiding air bubbles will probably be a bigger problem than any of your present concerns.

Jim


Damn! I was right again.

Jim


Jim,

I need to get a grand piano. An old Steinway would do just fine. And the time to learn Rachmaninov's Piano Concerto No 3.

Evan

#49 Mark C.

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Posted 28 June 2013 - 11:16 PM

After you get that Grand piano cut the top into some coddle boards and save a large square for the bottom of mold.This top may have stain rings from some of Jims vitracation experiments that weeped thru.The rings will not bother the mold process-stick to major brands like Stienway or Baldwin as they have a smoother wood finish.
As far as brands of green soap any green soap will do-better still is mold release sold at ceramic suppliers.Green soap will leave a small foam but it will not show once plaster is poured.
Mark
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#50 Benzine

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Posted 29 June 2013 - 11:12 AM

Just ignore Jim. Most of us do. But I find him funny, so I don't. I do know how to cast plaster though.Mark Cortnoy has good advice.
TJR.


I definitely don't ignore Jim. He's got some of the best stories on these forums, not to mentioned, I'm a fan of his work.
"Anything worth believing, is worth questioning"

#51 Strelnikov

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Posted 29 June 2013 - 12:01 PM

After you get that Grand piano cut the top into some coddle boards and save a large square for the bottom of mold.This top may have stain rings from some of Jims vitracation experiments that weeped thru.The rings will not bother the mold process-stick to major brands like Stienway or Baldwin as they have a smoother wood finish.
As far as brands of green soap any green soap will do-better still is mold release sold at ceramic suppliers.Green soap will leave a small foam but it will not show once plaster is poured.
Mark


I'm going to try Murphy's Oil Soap next and pull the boards sooner than I did the first time. The vaseline didn't work so good. There were places where the plaster stuck to the wood even where I put on a liberal coating of vaseline.

Evan

#52 Biglou13

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Posted 29 June 2013 - 01:09 PM

Never made a flat mold I wonder if alcohol water spray might help. Also how Did you mix plaster.?
Caution big brother is watching.
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#53 OffCenter

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Posted 29 June 2013 - 03:33 PM


Just ignore Jim. Most of us do. But I find him funny, so I don't. I do know how to cast plaster though.Mark Cortnoy has good advice.
TJR.


I definitely don't ignore Jim. He's got some of the best stories on these forums, not to mentioned, I'm a fan of his work.


That's awfully nice of you to say that, Benzine. I guess you're not such a bad guy after all.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#54 BeckyH

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Posted 29 June 2013 - 05:22 PM

Remember, you need a collar or reservoir for your slip when pouring the mold. The water in the slip will get sucked into the plaster, and the level of the slip in the mold will go down. You need a big enough space at the top of the mold to hold the extra slip. I like to plug the top of the object I'm casting and pour a slab about 2" deep. When it is just cool I cut a pour gate that just matches the top of the object. You need to cut keys in the main part of the mold- just a few depressions about the size and shape of 1/2 of a quarter- before casting the top, so that the parts fit together properly. Then strap them together to fully dry before making your first casting. It is easy enough to clean up the cast piece with a sponge if the surface is a bit bubbled.

#55 Strelnikov

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Posted 29 June 2013 - 06:56 PM

Remember, you need a collar or reservoir for your slip when pouring the mold. The water in the slip will get sucked into the plaster, and the level of the slip in the mold will go down. You need a big enough space at the top of the mold to hold the extra slip. I like to plug the top of the object I'm casting and pour a slab about 2" deep. When it is just cool I cut a pour gate that just matches the top of the object. You need to cut keys in the main part of the mold- just a few depressions about the size and shape of 1/2 of a quarter- before casting the top, so that the parts fit together properly. Then strap them together to fully dry before making your first casting. It is easy enough to clean up the cast piece with a sponge if the surface is a bit bubbled.


I'm a bit confused but I think you're talking about a 2-piece mold. I am making a simple 1-piece mold.

Evan

#56 Strelnikov

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Posted 29 June 2013 - 07:00 PM

Never made a flat mold I wonder if alcohol water spray might help. Also how Did you mix plaster.?


I made another mold and used Murphy's Oil Soap instead of vaseline as the release agent. It worked much better than the vaseline.

I mixed the plaster with a paint mixer powered by an electric drill.

I jiggled and shook the mold and a bunch of air bubbles came to the top but I still had some air bubbles at the bottom of the mold as before.

Evan

#57 Benzine

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Posted 30 June 2013 - 08:25 AM



Just ignore Jim. Most of us do. But I find him funny, so I don't. I do know how to cast plaster though.Mark Cortnoy has good advice.
TJR.


I definitely don't ignore Jim. He's got some of the best stories on these forums, not to mentioned, I'm a fan of his work.


That's awfully nice of you to say that, Benzine. I guess you're not such a bad guy after all.

Jim


Oh, don't let my comment fool you. I'm a huge ########, just ask my wife, friends, family and students.
"Anything worth believing, is worth questioning"

#58 Strelnikov

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Posted 01 July 2013 - 08:10 PM

With Murphy's soap I don't use a brush, I use a small piece old t shirt.

I started with brush to many bubbles, then wiped bubbles with t shirt rag.... Now I just use small square of t shirt.

If any small bubbles I wipe off with moist oils soap rag.


I found out that if I pour the Murphy's soap on the object to be coated and spread it out with a foam brush it doesn't make bubbles.

When I got the bubbles I poured the Murphy's soap into a dish and used a wetted sponge to spread the soap from the dish onto the object to be coated.

Evan




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