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Mixing plaster


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#1 Strelnikov

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Posted 27 June 2013 - 11:02 AM

Next thing I need to figure out is how much plaster to mix. The volume of my box minus the volume of the bowl I'm making is 864 cu in which is 3.74 gallons which is 31.3 lb of water. For that amount of water I need 44.7 lb of plaster. But that will make too much because adding the plaster to the water will increase the total volume. So how much water and plaster do I need to fill my 3.74 gallon box?

Thanks,
Evan

#2 neilestrick

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Posted 27 June 2013 - 11:30 AM

For Pottery Plaster #1, you will need 16.316 grams of dry plaster for each cubic inch. Add water accordingly.
Neil Estrick
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#3 Marcia Selsor

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Posted 27 June 2013 - 11:50 AM

If you go to the manufacturers website you will find all kinds of information about plaster and how to mix it.
US Gypsum

http://www.usg.com/r...a-en-IG1366.pdf

Marcia

#4 Strelnikov

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Posted 27 June 2013 - 01:07 PM

Thanks, I have the PDF spec sheet for USG No 1 Pottery Plaster but it doesn't tell how much water and plaster it takes to fill one gallon of volume. The ratio of plaster to water is 10 to 7. If I start out with one gallon of water and add the correct amount of plaster then what total volume do I end up with?

Evan

#5 Strelnikov

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Posted 27 June 2013 - 01:11 PM

For Pottery Plaster #1, you will need 16.316 grams of dry plaster for each cubic inch. Add water accordingly.


Does 16.316 grams of dry plaster plus the correct amount of water make one cubic inch of volume?

Evan

#6 neilestrick

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Posted 27 June 2013 - 02:26 PM


For Pottery Plaster #1, you will need 16.316 grams of dry plaster for each cubic inch. Add water accordingly.


Does 16.316 grams of dry plaster plus the correct amount of water make one cubic inch of volume?

Evan


Apparently so. I calculated this formula from info from US Gypsum. It has always worked for me.
Neil Estrick
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Owner, Neil Estrick Gallery, LLC
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#7 Strelnikov

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Posted 27 June 2013 - 06:45 PM



For Pottery Plaster #1, you will need 16.316 grams of dry plaster for each cubic inch. Add water accordingly.


Does 16.316 grams of dry plaster plus the correct amount of water make one cubic inch of volume?

Evan


Apparently so. I calculated this formula from info from US Gypsum. It has always worked for me.


Super, thanks very much Neil. I'll let everyone know how my first mold goes.

Evan

#8 Mart

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Posted 28 June 2013 - 03:38 PM

For start, convert your first measurements to metric system and it all becomes really easy. After you have completed the calculations, convert it back to imperial pint, gallon, lbs and you are set.

#9 Strelnikov

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Posted 28 June 2013 - 04:02 PM

Thanks, the amount of plaster I mixed for my first mold was ideal. Not too much,not too little, just a bit left over.

Evan

#10 DanMehlman

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Posted 23 July 2013 - 07:36 AM

Cubic inches divided by 75 = quarts of water

 

1 quart of water (2 lbs) is mixed with 3 lbs plaster

 

 

 

 

 

 

 

Dan Mehlman

www.Mehlmandesign.com



#11 DanMehlman

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Posted 23 July 2013 - 07:37 AM

I'm sorry, that wasn't clearly stated.

Cu. in. divided by 75= the quarts of water you should use in the mix.



#12 Les

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Posted 23 July 2013 - 10:05 PM

This may help you with volumes:

https://www.dropbox....ster Mixing.doc

#13 cync329

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Posted 25 July 2013 - 09:56 AM

Thank you, Les, for the plaster to water chart.  I have used plaster of paris from Home Depot and a silicone cake pan to make bats.  The cake pan is great because I don't need a release agent to get the bat out.  I've tried to mix the plaster as I was taught in art college decades ago, but I've forgotten details. 

 

Cynthia

intermediate level potter



#14 Mark C.

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Posted 25 July 2013 - 10:21 AM

I use a power mixer to mix the plaster for two to 3 minutes  then I drop the bucket a few tomes on the floor to raise the bubbles to the top before pouring it.

I throw on plaster bats and pie pan in two sizes are what I use.The ones in the photo are 6 inch pans.

Mark


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#15 Marcia Selsor

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Posted 25 July 2013 - 11:52 AM

After I mix with a drill and mixer, I let it sit, tapping the sides. Much the same a bouncing on the floor like Mark. If you still have and bubbles coming up, have a squirt bottle standing by with diluted alcohol. Squirt the bubbles before pouring the plaster into your mold. The bubbles disappear instantly with the alcohol.

Marcia

#16 oldlady

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Posted 25 July 2013 - 08:28 PM

yea Marcia,  lots of uses for rubbing alcohol.  does anyone ever use it as intended.  saw a youtube about dripping one drop onto freshly glazed pieces to make permanent  wet looking spots.   not my  thing but might be yours> 


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