Bunny Lemak on fri 22 sep 06
Hello all!
Since it is now cool enough in the mornings to work outside, I thought I
would make some hump/slump molds this morning......oh my what a mess I
made!
The first two attempts came out perfect, except for being a little sloppy,
but the next few attempts were a nightmare! I have no idea what I did
differently, if that or maybe it just got warmer and the plaster got dried
up on me quicker??? I have no idea, but I would LOVE to hear any
suggestions on making this. Oh, btw the first 2 pieces were small, then I
atempted to do someting bigger and that is where I failed. Why????
I tried to look into the archives, but once again I have failed, maybe it
is because I have no clue as to what I am trying to look for?! Sorry our
family has had 1 heart attack and 1 major stroke in the last 10 days and
I'm the one running to 2 different hospitals, my husband made me take
today off before I ended up in the looney bin! I'm not thinking too well
these days! Sorry!
D. L. Engle on fri 22 sep 06
Hi Bunny,
You'd have to describe your method to get any feedback that may be helpful.
But one thing I can suggest is that plaster will set off faster is it is
mixed with dirty (plaster contaminated) water. Was your third batch mixed
with water that maybe got hands or tools rinsed off in it?
Best Wishes, Debbie
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Bunny Lemak
Sent: Friday, September 22, 2006 1:58 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Making plaster hump/slump molds - info needed.
Hello all!
Since it is now cool enough in the mornings to work outside, I thought I
would make some hump/slump molds this morning......oh my what a mess I
made!
The first two attempts came out perfect, except for being a little sloppy,
but the next few attempts were a nightmare! I have no idea what I did
differently, if that or maybe it just got warmer and the plaster got dried
up on me quicker??? I have no idea, but I would LOVE to hear any
suggestions on making this. Oh, btw the first 2 pieces were small, then I
atempted to do someting bigger and that is where I failed. Why????
Snail Scott on sat 23 sep 06
On Sep 22, 2006, at 3:57 PM, Bunny Lemak wrote:
> ...I thought I
> would make some hump/slump molds this morning......oh my what a mess I
> made!
> The first two attempts came out perfect, except for being a little
> sloppy,
> but the next few attempts were a nightmare! I have no idea what I did
> differently, if that or maybe it just got warmer and the plaster got
> dried
> up on me quicker??? I have no idea, but I would LOVE to hear any
> suggestions on making this. Oh, btw the first 2 pieces were small,
> then I
> atempted to do someting bigger and that is where I failed. Why?
Well, it is an odd phenomenon of plaster that
larger batches tend to set more quickly than
small ones. Also, the more you agitate the
plaster during mixing, the quicker it will set,
so although most people don't agitate a big
batch as thoroughly, maybe you tried to make
up for it and get it _really_ well mixed? It
naturally seems like it ought to take longer to
mix a big batch, but it's not really true. It's
also easy to lose track of how much longer
it takes to add the plaster to the water when
making a larger batch, if you are using a
small scoop. Though plaster doesn't really
start to set while it's just slaking, many people
accidentally agitate the bucket while adding
the plaster, thus unwittingly starting the mixing
time 'clock' ahead of schedule, so by the time
they start consciously mixing it, it's already
partway through its chemical reaction. It's also
easy to get distracted by a larger mold,
tweaking something or another while your
'plaster clock' is ticking, or pouring the mix
slowly while you wrestle a larger bucket.
Also: Was the water that you used to mix the
first small batches lukewarm only because the
hot water hadn't reached your faucet in full
force yet? The same faucet setting, running
for longer because you were filling a bigger
bucket, would give hotter water by the time
you were done. (Seen this happen!) If you
don't check and add more cold if needed,
you could cut setting time in half. The water
temperature is the single biggest variable
in plaster setting time. Pros use a thermometer
to keep this under control, because even five
or ten degrees can make a noticeable
difference in set time. Putting your hand in
and guessing works well enough most of the
time, but be attentive to what your hand is
telling you. When in doubt, keep it cooler.
By the way, how much time elapsed between
the first molds and the latest effort? Older plaster
absorbs moisture from the air, and is 'primed'
to set more quickly when mixing begins. In a
humid climate, a matter of weeks can make a
difference, especially if it wasn't really fresh to
start with. Eventually, plaster can get so fully
re-humidified that is sets up while still in powder
form and becomes useless, but right before it
hits that point, it can start setting up scary-fast.
I don't know if any of these factors is relevant
to your process, but there could be more than
one, contributing in their own minor way to
the detriment of the whole shebang.
So: make sure you add the plaster to the
water in a smooth but fast, efficient way. Make
sure you don't jostle or agitate the bucket
while the plaster is slaking. Mix thoroughly
but not frenetically. Use slightly cooler water
for a longer open time. And use plaster that
hasn't been sitting around for months, whether
at your studio or at the supplier's warehouse.
Good luck with the next effort! Plaster can
be squirrely, but it's not rocket science either;
you'll get it worked out OK.
-Snail
Snail Scott on sat 23 sep 06
On Sep 22, 2006, at 7:26 PM, D. L. Engle wrote:
> ...plaster will set off faster is it is
> mixed with dirty (plaster contaminated) water...
Another good point, D.L. A bucket with recently
set plaster residue can catalyze the next batch
made in it. Use clean tools!
-Snail
Bunny Lemak on sun 24 sep 06
Thanks Debbie & Snail-
I do believe I found a few mistakes that I made, yes I'm pretty sure the
second batch was mixed in the "dirty" bowl from the first, and I refilled
my pitcher of water via the outside hose, which was in the sun all
morning, so therefore it was extremly warm water.
I tried again yesterday morning, and had much better success, not only did
I rinse out my tools inbetween batches, but I made sure I used water from
inside the house (cooler!). What a difference this all made.
I also added water to the bowl before adding the plaster - SO much better
to work with!!
Thank you! I knew I was doing something wrong - just couldn't figure it
out!!
I appreciate both answers!
Bunny
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