Ingeborg Foco on sat 22 jan 05
Thanks to everyone on your plaster inputs and Wayne thanks for the correct
spelling of "efflorescence". I hate it when I misspell a word! We were
seriously considering buying a place in the keys until we saw the rusting
and spalling caused by salt water/cement mix. After checking with our
structural engineer, we decided to pass on that house. As for flooring
Wayne, my brick paver efflorescence problem was solved by washing the floor
with muriatic acid. A couple of washings took care of the problem . Since
the pavers weren't grouted, I didn't have to worry about weakening the
grout. Nasty stuff though.
The water I use here comes from the island RO plant. In my opinion it is
about as inert as water can get; no minerals just a bit of chlorine to make
sure there are no bugs. Salt in the clay was something that never occurred
to me. When I lived in Washington State, I used a variety of clay bodies
over the years. When a ton was used up, I usually tried something else and
I never had problems with my plaster table. Now I am wondering if in
addition to the clay it could be the salt in the air.....My shop is situated
one mile from the bay and my building is 25 feet from a salt water canal..
Everything corrodes around here from the harsh environment; you can almost
watch things rust.
Michael, yes I have changed clay suppliers. The first year I tried clay
from one supplier and now I'm with someone else. Makes me wonder now!!! By
the way, I have been wedging and "rodding" plates all day. What a great
technique, can't thank you enough. I am having some difficulties with the
restand method though and replay that part of the video each night to see
what I am doing wrong. Eventually I will get it right!
For now I guess I will just keep cleaning the table and vacuuming underneath
and wait to see how bad it gets before I tear out and repour.
Ingeborg in SW Florida bracing for temperatures to reach in the 30's by
tomorrow. Times like these, having an open air studio can be somewhat
unpleasant. Thank goodness I didn't get rid of the ski underwear. Who
would have thought I would be wearing it underneath my jeans to work; today
wearing shorts and longjohns tomorrow!
the Potter's Workshop & Gallery
P.O. Box 510
3058 Stringfellow Road
St. James City, Florida 33956
239-283-2775
Ingeborg Foco on sat 22 jan 05
Good Morning,
I've been experiencing plaster problems that I can no longer ignore. Over
three years ago I built a plaster table for recycling clay and wedging. The
bottom of the table has 2" holes drilled into the plywood to facilitate
drying. It seemed fine for about a year and then I started noticing white
"fur" growing on top of the plaster when no clay was drying. It looked like
effervescent, something I experienced after laying a brick floor; after
several cleanings, the white scum stopped developing.
I have been vacuuming and wiping the stuff off the surface of the plaster
whenever I see it. If left for long periods of time, it grows quite "deep".
It is light and fluffy. Now however, I notice big stuff flaking off and
dropping out of the bottom holes . No amount of cleaning seems to stop this
process and it is getting worse.
When I mixed the plaster I know I measured the proportions of water to
plaster and don't think that is the problem. Prior to my move to SW
Florida, I had a plaster table for over 20 years and it was still good when
I moved. Regretfully I couldn't ship it here.
What could be causing this deterioration of plaster? I assume that is what
is happening. Is it some kind of tropical thing or did I inadvertently
purchase old plaster? Does anyone have any insight into this annoying
mystery. It appears that I will have to start all over again and would hope
that the next table will last for 20 years.
Thanks in advance to any and all suggestions/ideas.
Sincerely,
Ingeborg
the Potter's Workshop & Gallery
P.O. Box 510
3058 Stringfellow Road
St. James City, Florida 33956
239-283-2775
Kenneth D. Westfall on sat 22 jan 05
Your problem is more likely coming from the clay your drying not a problem
with the plaster. Salts from the water in the clay is being absorbed by
the plaster and then migrating to the surface as it drys.
Kenneth D. Westfall
Pine Hill Pottery
R.D. #2 Box 6AA
Harrisville, WV 26362
kenneth@pinehillpottery.com
http://www.pinehillpottery.com
RJ Shulenburg on sat 22 jan 05
My table is 6 years old and just started growing fuzzies this summer after I
started reclaiming porcelain clay on it. I've just been wiping it off. I
thought it might have something to do with the high humidity in Virginia
Beach. I don't have holes in the bottom of my table.
Ronda in Virginia
Clip
three years ago I built a plaster table for recycling clay and wedging. The
bottom of the table has 2" holes drilled into the plywood to facilitate
drying. It seemed fine for about a year and then I started noticing white
"fur" growing on top of the plaster when no clay was drying. It looked like
effervescent, something I experienced after laying a brick floor; after
several cleanings, the white scum stopped developing.
I have been vacuuming and wiping the stuff off the surface of the plaster
whenever I see it. If left for long periods of time, it grows quite "deep".
It is light and fluffy. Now however, I notice big stuff flaking off and
dropping out of the bottom holes . No amount of cleaning seems to stop this
process and it is getting worse. Sincerely,
Ingeborg
the Potter's Workshop & Gallery
P.O. Box 510
3058 Stringfellow Road
St. James City, Florida 33956
239-283-2775>
____________________________________________________________________________
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John Rodgers on sat 22 jan 05
I concur with Kenneth Westfalls post on this subject.
In the slip casting world, all plaster molds will eventually beging to
effervesce and grow "beards."
As more and more salts are absorbed by the plaster, the effervescence
get worse and eventually the salts will cause the breakdown of the
plaster and flaking of the material as it deteriorates.
The breakdown process can be ameliorated a bit by allowing thorough
drying between each use because excess moisture exacerbates the
situation. . But eventually the material will fail.
Regards,
John Rodgers
Chelsea, AL
Ingeborg Foco wrote:
>Good Morning,
>
>I've been experiencing plaster problems that I can no longer ignore. Over
>three years ago I built a plaster table for recycling clay and wedging. The
>bottom of the table has 2" holes drilled into the plywood to facilitate
>drying. It seemed fine for about a year and then I started noticing white
>"fur" growing on top of the plaster when no clay was drying. It looked like
>effervescent, something I experienced after laying a brick floor; after
>several cleanings, the white scum stopped developing.
>
>I have been vacuuming and wiping the stuff off the surface of the plaster
>whenever I see it. If left for long periods of time, it grows quite "deep".
>It is light and fluffy. Now however, I notice big stuff flaking off and
>dropping out of the bottom holes . No amount of cleaning seems to stop this
>process and it is getting worse.
>
>When I mixed the plaster I know I measured the proportions of water to
>plaster and don't think that is the problem. Prior to my move to SW
>Florida, I had a plaster table for over 20 years and it was still good when
>I moved. Regretfully I couldn't ship it here.
>
>What could be causing this deterioration of plaster? I assume that is what
>is happening. Is it some kind of tropical thing or did I inadvertently
>purchase old plaster? Does anyone have any insight into this annoying
>mystery. It appears that I will have to start all over again and would hope
>that the next table will last for 20 years.
>Thanks in advance to any and all suggestions/ideas.
>
>Sincerely,
>
>Ingeborg
>the Potter's Workshop & Gallery
>P.O. Box 510
>3058 Stringfellow Road
>St. James City, Florida 33956
>
>239-283-2775
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
>
ilene richardson on sat 22 jan 05
Your plaster is growing mold.
Put it in the oven at the lowest temperature until it feels dry... or =
dry it out in the sun for an entire day.
Then mist the surface with water and sodium benzoate, a preservative. It =
will get absorbed into the plaster way down deep and prevent mold from =
reoccurring.
Ilene
Michael Wendt on sat 22 jan 05
Ingeborg,
Do you still use the same clay supplier? Plaster absorbs some of the water
in the clay and that water contains dissolved minerals. When the water
evaporates from the table surface, the minerals are left on the surface of
the plaster. I suspect they are harmless if you simply remove them so they
don't get into your clay,
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Sheryl VanVleck-Wells on sun 23 jan 05
I used a cement board wedging table in DRY! DRY! Wyoming and had the =
same fuzzies problem.=20
Sheryl: Now in Indiana where I have to wait for things to dry rather =
than try to keep them damp. (Sigh! Never Happy)
www.VanVleckStudio.com 2,000 more hours =
and I will be done upgrading my internet site.
Janet Kaiser on sun 23 jan 05
What has someone in North Wales, UK got of
benefit to say to a potter in Florida, USA?!?!
Well, Ingeborg, the following two statements you
made, make a lot of sense to me when put together
:
>Now I am wondering if in addition to the clay
it could be the salt in the air..... My shop is
situated one mile from the bay and my building is
25 feet from a salt water canal. Everything
corrodes around here from the harsh environment;
you can almost watch things rust.
>Times like these, having an open air studio can
be somewhat unpleasant.
To expand on that: we are just feet from the
water's edge and air-borne salt is the bane of
our lives. Nothing made of untreated iron-based
metal can be left outside. Cars rust. Gates and
railings rust. The screws holding gutters, pipes
and windows rust. Hinges rust. Handles rust.
Nails holding slates to the very roofs corrode...
You get the idea. Talking to potters and their
husbands from Florida in 2003, they knew exactly
what the problem would be here without saying
more than a couple of words. They had also spent
time out on a Pacific Island and knew that even
in a benign climate, salt was still a killer. So
what chance have we, when the Soutwesterlies
bring in a hundred weight of salt per acre per
year?!
Salt is also hanging around in the air all the
time on the coast, so when the high humidity hits
and it is absorbed by plaster... Well you know,
it just builds up and up, so even drying it out
will leave a certain amount of salt in there.
And the clay...? Well, I do not see why salt
would not penetrate in exactly the same way,
especially if you have a lot hanging around for a
long time. Or it is being stored by your supplier
in a salty environment...
I have often posted about the effect coastal salt
has on unvitrified fired clay, never mind unfired
clay. I know there are land lubber sceptics who
do not believe me, but it will cause glaze to pop
off first, before it eats away from pockets which
have built up inside the body. This is the highly
saline mix we get from sea salt plus soft rain
water... High rainfall does not dilute the salt
enough and anyway, it is my theory it only makes
doubly sure maximum amounts of salt crystals are
introduced, so the clay effectively filters them
out and they build up into massive amounts, which
eventually have to burst forth somewhere, some
how...
Thanks to the Gulf Stream, frost damage is
negligible around here too, so it is all down to
moisture plus salt being the prime culprit. With
you being in an outdoor studio you are going to
notice even more stuff happening over time. Jeff
van den Boeck never did get back with a solution
for the problems in his jungle studio in the
Philippines... It was mould there, but basically
it is the same thing... Humidity. When the
climate does not allow for stuff to dry out
completely, there is going to be a problem. Find
a way of lowering the humidity levels and you may
solve the problem with salt too...
Airborne salt deposits feel greasy to the touch
and are the very devil to "wash" off. Wiping or
scrubbing with copious amounts of water helps,
but a power hose on full blast is quite effective
too. It is this coating which also corrodes the
surface of aluminium, weakens copper and brass
enough to eventually loose a lot of strength,
although it does not flake away completely like
iron. Galvanising is also not a solution... It is
that bad!
So my main advice to you, is to try to find a way
of protecting any plaster from general humidity
and airborne moisture... Maybe create a dry room?
Sincerely
Janet Kaiser -- off to clean the windows of salt!
Just a few days worth, but hard to see out!
**************************************************
**********
THE CHAPEL OF ART - or - CAPEL CELFYDDYD
8 Marine Crescent : Criccieth : GB-Wales LL52 0EA
Tel: ++44 (01766) 523122
http://www.the-coa.org.uk
Contact: Janet Kaiser: The International Potters
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Eleanora Eden on mon 21 feb 05
By mixing in equal parts clay, ashes, and sand or dirt, for an art
project once, made a slurry which when dry, grew what I thought was a
really beautiful crystalline growth kind of like ryme ice....I was
inviting this process you're talking about.
I notice when my molds are drying sometimes this fuzzy surface but it
doesn't seem to deteriorate the plaster and has never been a problem.
Never connected these two processes.
Eleanora
Dominic Spencer on sun 30 oct 05
Hello again people!
I've been experimenting with plaster casting, making casts of baby feet in
soft clay then taking a plaster cast of the impression, creating a
(positive) 3D plaster wall hanging. I am using red clay because I want to
utilise the colour deposit on the plaster surface to enhance the finished
product, creating a tonal effect on the feet, but taking the red deposit
off on the surface around the feet - creating a contrasting
white "mount". However
this has created problems in itself, because I have been getting tide
marks - a little like contour lines on an ordnance survey map - where I pour
the plaster, and at some other points on the surface, where the plaster
flows. I have used abrasive sponge to take the red clay deposit off where I
don't want it, but these tide marks go deep into the plaster, and I haven't
yet been able to reproduce a uniform whiteness surrounding the feet, without
these marks remaining. To sand the plaster down to the point where the
marks disappear means I end up with places that are more deeply eroded than
the surrounding surface, which is not desirable, it needs to be a generally
flat surface surrounding the feet.
I have tried:
- altering the plaster mix - both weak and strong - warmer and colder water
- harder and softer clay
- leaving the clay till leather hard before pouring
- leaving the clay till dry before pouring
but none of the above have made any difference - the tide marks persist.
I know this isn't really a problem one would have with plaster mould making,
as tide marks wouldn't matter - but I wondered if there was a plaster expert
out there who would be able to enrich me with the benfit of his or her
greater wisdom!!
Many thanks for reading - and even more thanks for replying!!
Dominic
www.agpstudio.co.uk on sun 30 oct 05
Hi Dominic,
I think that you should be 'tamping' the plaster as soon as you have poured
it - that is:
bouncing your fingers [held close together] up and down _just_ below the
surface of the liquid plaster - but not above and hitting the surface, as
that will cause bubbles.
This creates pressure waves that will should [hopefully], cure your problem
and also bounce any air bubbles from the surface of the clay. Whilst you are
tamping move your hand around the cast so that the effect is evenly
distributed.
This needs to be done before the plaster gets too stiff and you need to make
sure that you do not hit the clay model when doing it !!
Regards,
Alistair Gillies
From: "Dominic Spencer"
> Hello again people!
I am using red clay because I want to
> utilise the colour deposit on the plaster surface to enhance the finished
> product, creating a tonal effect on the feet, but taking the red deposit
> off on the surface around the feet - creating a contrasting
> white "mount". However
> this has created problems in itself, because I have been getting tide
> marks - a little like contour lines on an ordnance survey map - where I
> pour
> the plaster, and at some other points on the surface, where the plaster
> flows. > I have tried:
>
> - altering the plaster mix - both weak and strong - warmer and colder
> water
> - harder and softer clay
> - leaving the clay till leather hard before pouring
> - leaving the clay till dry before pouring
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