PaperClay - water resistant?!?

Anyone have any suggestions? I'm going to start with paperclay but i need it to be water resistant...

The same problem I have with clay fired with glaze at RAKU :/

Thank you in advance! Vitold

I know paper clay is different than the link I am sending you - but Charmaine will know of these issues more than 'artists' cuz she deals with real world and building code, construction level techniques:

There are two different stuffs called paper clay.

One is paper pulp+glue (papier mache). It is not waterproof unless you use f.ex epoxy glue.

The pther is normal water based clay with cellulose pulp added. When fired, the organic stuff burns out leaving very porous and lightweight ceramic form. It is waterproof in the sense that it does not dissolve in water, but because of porosity it is less waterproof than ordinary bisque fired clay. I *guess* one can glaze it so it becomes not-permeable.

-lauri

I use clay mixed with paper (cellulose). It is ordinary bisque fired first and then fired with glaze but in raku technique - so the glaze is very "cracle" and very water unresistant :-) What to use to make for ex a vase resistant? Vitold

Lauri Levanto wrote:

Unfortunately I can't help more with glazes. I am a glass artist and use paper clay only to make bisque fired moulds.

All i know is that you have to match the shrinkage of the glaze with the body.

-lauri

You might try polyurethane on the inside of your vase. I know that Marine Spar polyurethane makes wood pretty much impervious to water.

The only thing that I know will work, because I do it professionally, is to seal with an epoxy resin putty, the putty would be colored to match or become the glaze, then spray the whole thing with a special 'aliphatic' urethane to protect the epoxy. A lot of work. Epoxy is 100% effect as a water vapour barrier. If it chips, or cracks - then all that work is wasted until it is repaired.

This is a very common problem - people see those giant, inexpensive glazed pots coming out of Asia - only to find they last less than one season outside. The have to be sealed inside, but also outside because of the poor, microcracked glazing, and often the pots themselves are not 'high' fired and therefore very fragile.

It is very important to use clay and glaze that match; in other words don't use earthenware glaze on a stoneware clay. Granted the matrix of a paperclay body is more open than your average smooth clay, but then so is a coarse crank or sculptural body, and they can be glazed very successfully.

TEST! Sort out what clay you are going to use, make a small test pot, buy a small amount of an appropriate brush-on glaze, follow the instructions on the label, and fire the result to the recommended cone. If it holds water you're there, if not, by following the above you have taken a course that can be checked at each stage which should allow you to isolate what went wrong.

Steve Bath UK

In article , snipped-for-privacy@gmail.com writes

if you're using a cone 10 claybody with paperclay added & fire the final piece to cone 10 you will be fine with a water containing vessle.

if you fire to raku temps, you'll see water ooze thru.

i fired lately some sawdust clay. cone 10. works fine! the cool part to me is the pieces are a lot lighter then typical.

see ya

steve

Steve Mills wrote:

Hello, I use paper clay for my prototypes of my "heat retentive plate" because that allows me to manipulate the raw parts safely. If you want them water resistant you have to glaze them. Juan

snipped-for-privacy@gmail.com wrote:

Has it been used?