Timothy Joko-Veltman on fri 15 aug 08
A while ago, I asked about the difference between standard/pure
plaster and Pottery Plaster #1, and I ended up being given the idea of
adding around 5% cement to the mix to harden it up some. Well, I
didn't buy a bag of Portland cement, but I did find a white grout at
the local construction store. The first ingredient listed
(translated) is: "gray or white Portland cement". I figured it would
have to do, and I tried it. Made a few slabs for drying clay, a few
small one-piece molds ... a large hump mold. So far, it's working
rather well. The plaster is definitely more resistant to wear, and
yet porous enough for my needs (which admittedly, are few at the
moment).
Here is what I did:
1. Prepared: cottle and/or prototype for the mold.
2. Measured out water; I used 5L (~10.56pints) for the large hump mold
and a drying slab.
3. Weighed out the plaster (7kg (~15.43lb)) and grout (5% of 7kg =
350g (~12.35oz.)).
4. Transferred the dry ingredients to a large durable plastic bag,
twisted the mouth closed, and rolled it around and flipped it over a
couple times to mix the plaster and grout together.
5. Added the plaster slowly to the water - not dumping it in all at once.
6. Let the plaster soak for a minute or two.
7. Took out my drill with the paint-mixer on it, and mixed the
plaster for about 30 seconds (vortexes = bubbles! Don't make them!).
Then finished the mixing with my hand or a large spoon.
8. Poured plaster carefully into cottle and ... let stiffen.
9. Removed the plaster from the cottle when it was starting to feel
warm, and scraped the corners down and rounded the edges.
Regards,
Tim
Dawn Kleinman on sat 16 aug 08
I am in the process of trying to come up with the best way to dry out my
clay. I had a plaster table that I had made. I probably used your basic
plaster of paris. It has chipped and flaked no matter how careful I had
been. Sometimes I didn't need to scrape the clay if I let it sit long
enough. The problem is that it sometimes peeled off the plaster as well. So
I have been researching... I like your idea. I had thought of cement but I
didn't think it would be porous enough. Never thought of mixing it.
Thanx
Dawn
- where I'm on my 3rd electrician and none have shown up - even after
they had each spent an hour taking measurements and talking up the job. So,
if you're near Philly and know someone you could recommend, let me know.
On Fri, Aug 15, 2008 at 5:31 PM, Timothy Joko-Veltman <
ceramista.tim@gmail.com> wrote:
> A while ago, I asked about the difference between standard/pure
> plaster and Pottery Plaster #1, and I ended up being given the idea of
> adding around 5% cement to the mix to harden it up some. Well, I
> didn't buy a bag of Portland cement, but I did find a white grout at
> the local construction store. The first ingredient listed
> (translated) is: "gray or white Portland cement". I figured it would
> have to do, and I tried it. Made a few slabs for drying clay, a few
> small one-piece molds ... a large hump mold. So far, it's working
> rather well. The plaster is definitely more resistant to wear, and
> yet porous enough for my needs (which admittedly, are few at the
> moment).
>
> Here is what I did:
>
> 1. Prepared: cottle and/or prototype for the mold.
> 2. Measured out water; I used 5L (~10.56pints) for the large hump mold
> and a drying slab.
> 3. Weighed out the plaster (7kg (~15.43lb)) and grout (5% of 7kg =
> 350g (~12.35oz.)).
> 4. Transferred the dry ingredients to a large durable plastic bag,
> twisted the mouth closed, and rolled it around and flipped it over a
> couple times to mix the plaster and grout together.
> 5. Added the plaster slowly to the water - not dumping it in all at once.
> 6. Let the plaster soak for a minute or two.
> 7. Took out my drill with the paint-mixer on it, and mixed the
> plaster for about 30 seconds (vortexes = bubbles! Don't make them!).
> Then finished the mixing with my hand or a large spoon.
> 8. Poured plaster carefully into cottle and ... let stiffen.
> 9. Removed the plaster from the cottle when it was starting to feel
> warm, and scraped the corners down and rounded the edges.
>
> Regards,
>
> Tim
>
David Woof on sat 16 aug 08
Dawn=2C I think home made plaster is an interesting topic and have read ev=
eryone's experiments and experiences with interest=2C but there is a simpl=
e and better way to=20
reclaim scrap clay than plaster with the risk of plaster contamination to t=
he clay=20
and associated problems.
=20
Cut off the legs of cast off denim jeans or use small canvas bags. Tie the=
cuff ends=2C=20
fill with scrap clay slop to a comfortable lifting weight. Fold over top e=
nd=2C bunch up=2C=20
and secure with a heavy duty slip knot cord with which to hang the "leg" of=
clay.
=20
The "leg" will drip and water will evaporate from the surface. Depending=
=20
on enviromental humidity it can take one to several days to reach=20
wedging consistancy. Give the "leg" a squeeze in passing twice a=20
day until you feel the clay becoming firm. Then peel the cloth away=20
and wedge clay that is almost filter press yummy.
=20
I never use plaster for wedging unless it is covered with canvas=2C=20
and any clay that has contact with plaster molds does not get=20
back into the recycle for throwing pots. I use that mold scrap=20
clay for rugged work where surface pop outs and blemishes
will just add welcome texture. =20
Part of my safe studio practice.
=20
David
=20
David Woof Studio
Clarkdale=2C AZ
Dawn wrote:_______________________________________________4a. Re: Home-made=
pottery plasterPosted by: "Dawn Kleinman" dkpottery@GMAIL.COM Date: Sat Au=
g 16=2C 2008 10:10 am ((PDT)) "I am in the process of trying to come up wit=
h the best way to dry out myclay. I had a plaster table that I had made. I =
probably used your basicplaster of paris. It has chipped and flaked no matt=
er how careful I had "_____________________________________________________=
_________
_________________________________________________________________
Get thousands of games on your PC=2C your mobile phone=2C and the web with =
Windows=AE.
http://clk.atdmt.com/MRT/go/108588800/direct/01/=
L TURNER on sat 16 aug 08
Dawn,
I have two methods for drying clay without plaster and they both work fine.
Which I use depends on how much there is.
1. I have several terracotta flower pot saucers from the garden center. My
largest is 10 inch, but larger sizes are available. I clean and dry them
thoroughly. Add the clay and leave it be just like plaster. After a while,
I use a wooden or hard rubber rib to reposition the wetter clay to either
the air surface or the saucer surface. If I were using porcelain, I might
use a thin cotton cloth to keep avoid having to scrape.
2. I use 12 and 16 inch square concrete patio stepping slabs covered with a
heavy cotton cloth (whatever heavy stuff I can find on the buck a yard table
at Walmart). Spread the clay out and wait. In fact I use these for
portable wedging slabs. When finished drying clay, set them aside and let
them dry. I did try using the concrete slabs without the cloth layer. It
does work, but the rough surface holds too much clay which requires a lot of
effort to clean up. The cloth works fine. I have never tried canvas as a
cover, but It would probably work as just as well.
Regards,
L. Turner,
The Woodlands, TX
Timothy Joko-Veltman on sat 16 aug 08
Dawn,
Maybe you just need a higher plaster to water ratio ... first slab I
made had too much water in it and was very soft ... just increasing
the amount of plaster made a big difference.
Tim
On Sat, Aug 16, 2008 at 10:21 AM, Dawn Kleinman wrote:
> I am in the process of trying to come up with the best way to dry out my
> clay. I had a plaster table that I had made. I probably used your basic
> plaster of paris. It has chipped and flaked no matter how careful I had
> been. Sometimes I didn't need to scrape the clay if I let it sit long
> enough. The problem is that it sometimes peeled off the plaster as well. So
> I have been researching... I like your idea. I had thought of cement but I
> didn't think it would be porous enough. Never thought of mixing it.
>
> Thanx
> Dawn
> - where I'm on my 3rd electrician and none have shown up - even after
> they had each spent an hour taking measurements and talking up the job. So,
> if you're near Philly and know someone you could recommend, let me know.
>
>
>
> On Fri, Aug 15, 2008 at 5:31 PM, Timothy Joko-Veltman <
> ceramista.tim@gmail.com> wrote:
>
>> A while ago, I asked about the difference between standard/pure
>> plaster and Pottery Plaster #1, and I ended up being given the idea of
>> adding around 5% cement to the mix to harden it up some. Well, I
>> didn't buy a bag of Portland cement, but I did find a white grout at
>> the local construction store. The first ingredient listed
>> (translated) is: "gray or white Portland cement". I figured it would
>> have to do, and I tried it. Made a few slabs for drying clay, a few
>> small one-piece molds ... a large hump mold. So far, it's working
>> rather well. The plaster is definitely more resistant to wear, and
>> yet porous enough for my needs (which admittedly, are few at the
>> moment).
>>
>> Here is what I did:
>>
>> 1. Prepared: cottle and/or prototype for the mold.
>> 2. Measured out water; I used 5L (~10.56pints) for the large hump mold
>> and a drying slab.
>> 3. Weighed out the plaster (7kg (~15.43lb)) and grout (5% of 7kg =
>> 350g (~12.35oz.)).
>> 4. Transferred the dry ingredients to a large durable plastic bag,
>> twisted the mouth closed, and rolled it around and flipped it over a
>> couple times to mix the plaster and grout together.
>> 5. Added the plaster slowly to the water - not dumping it in all at once.
>> 6. Let the plaster soak for a minute or two.
>> 7. Took out my drill with the paint-mixer on it, and mixed the
>> plaster for about 30 seconds (vortexes = bubbles! Don't make them!).
>> Then finished the mixing with my hand or a large spoon.
>> 8. Poured plaster carefully into cottle and ... let stiffen.
>> 9. Removed the plaster from the cottle when it was starting to feel
>> warm, and scraped the corners down and rounded the edges.
>>
>> Regards,
>>
>> Tim
>>
>
fran johnson on sun 17 aug 08
I have a plaster slab I use in my basement to dry reclaimed clay/slurry. It is 35 years+ old. It was made with plaster of paris-didn't know better. The plaster slab is on a raised wooden slat platform-2x4s on edge with half inch slats- so it has air circulation under it. I use old jeans legs cut open between the plaster and slurry. I've used lighter weight material but think the denim is better.
If my timing is good, I use the denim to fold the clay over on itself and wrap the clay in plastic. If it gets a little too hard I fold it and wrap the denim around it, wet the fabric and put the wrapped clay in plastic. Check consistancy in a day or so and add more water if necessary.
In my new studio I have concrete patio squares, one each for stoneware and porcelain. I treat them the same way. Drying time is different than the plaster but both do the job.
Fran
--- On Sat, 8/16/08, Des & Jan Howard wrote:
> From: Des & Jan Howard
> Subject: Re: Home-made pottery plaster
> To: "Clayart"
> Date: Saturday, August 16, 2008, 5:47 PM
> Dawn
> I gather the plaster absorbency is still valid. In which
> case cover the
> slab with a thin cotton layer, an old bedsheet perhaps.To
> reduce
> deterioration of the plaster by excess water spread the
> clay slop/sludge
> over the slab in groups about the size & weight of a
> cow pat (don't
> ask!). As soon as a skin forms on the bottom of the pat,
> jam roll it,
> bend it into a horseshoe & let this airdry.
> Des
>
> Dawn Kleinman wrote:
> > I am in the process of trying to come up with the best
> way to dry out my
> > clay. I had a plaster table that I had made. I
> probably used your basic
> > plaster of paris. It has chipped and flaked no matter
> how careful I had
> > been. Sometimes I didn't need to scrape the clay
> if I let it sit long
> > enough. The problem is that it sometimes peeled off
> the plaster as well. So
> > I have been researching... I like your idea. I had
> thought of cement but I
> > didn't think it would be porous enough. Never
> thought of mixing it.
>
> --
> Des & Jan Howard
> Lue Pottery
> Lue NSW
> Australia
> 2850
>
> 02 6373 6419
> www.luepottery.hwy.com.au
Des & Jan Howard on sun 17 aug 08
Dawn
I gather the plaster absorbency is still valid. In which case cover the
slab with a thin cotton layer, an old bedsheet perhaps.To reduce
deterioration of the plaster by excess water spread the clay slop/sludge
over the slab in groups about the size & weight of a cow pat (don't
ask!). As soon as a skin forms on the bottom of the pat, jam roll it,
bend it into a horseshoe & let this airdry.
Des
Dawn Kleinman wrote:
> I am in the process of trying to come up with the best way to dry out my
> clay. I had a plaster table that I had made. I probably used your basic
> plaster of paris. It has chipped and flaked no matter how careful I had
> been. Sometimes I didn't need to scrape the clay if I let it sit long
> enough. The problem is that it sometimes peeled off the plaster as well. So
> I have been researching... I like your idea. I had thought of cement but I
> didn't think it would be porous enough. Never thought of mixing it.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
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