Question for mud slingers

[Paul Tarlow]

I've been trying to make some clay molds and I'm having a heck of a time just drying the things.

Typically they are an inch or less thick (some are that thick because I'm intending to use the for low-relief casting).

I'd appreciate advice on drying them -- I keep drying them -- or they sit almost completely sealed in plastic for weeks.

Thanks in advance for any suggestions

- Paul

[ruthelf1030]

HI Paul,
I spent the better part of a year trying to make my own molds.
What a mess. I used the local high school's equipment which
is excellent, but I had to quit trying. Here is why:
1. There are many different types of clay bodies all of which have their own preferred drying and firing schedules, moisture levels.
2. Clay consistencies really vary a lot from batch to batch.
A person needs something called a "pugger" really badly to work
out clay moisture consistency problems, and even that is no gaurantee.
The wrap and save method does not distribute moisture evenly through the raw clay body - only repeated trips through the pugger can do that.
3. Slabbers are a wonderful piece of equipment - pricey.
4. Clay wheels for throwing are wonderful, the nice ones are spendy.
5. Getting the right moisture content - evenicity - while working the clay
is a major unknown., hence:
6. cracking, even with the possession of a majorly expensive professional clay drying cubbard.
I did learn that the smaller and less thick the casting item, the less chance of cracking, although no matter what I did with my bowls and plates, there was some cracking in the base.
After about 6 months of working with clay, I lessoned the cracks, per batch, but ugg, the work and the time!
Good luck - I hope you better luck then I had - I only came out with about 6 useable molds and they are nothing to brag about. Hopefully you will do better than me.
Regards and good luck
Ruth Elfering

[jerry flanary]

I know potters who cover huge platters completely with plastic and remove the plastic for an hour or so everyday. I believe the surface drys a bit then as it is recovered w/ plastic the dry surface pulls moisture out of the interior. This process takes a couple of weeks I think. The room is not too warm (room temperature!)

[ruthelf1030]

Hi Paul again,
While sucking on coffee here and trying to talk myself into getting my car washed, I thought of a few more things.
We have a wonderful artist here in central Minnesota who has his work in the Smithsonian and all over the place. He makes his raw clay-sand-body-before adding water, from scratch.
Can you find and make friends with someone like that.
There are high schools with majorly wonderful art teachers who can teach the skill of working with clay and may even to the work for you (make friend).
Moisture in clay working is kind of like this.
There is an elderly lady in Freeport MN who makes bread from scratch:
She can tell whether the day is too humid to make it, she can just feel it and tell whether more flour, oil, etc., is needed, and how much more needing is needed. I could not learn this just watching her.
Clay is kind of like this: adding moisture to ones hands while working it, is very touchy - too much and the piece is shot, too little and a person does not get the result they want, and slip (clay glue for addings pieces to the main body) is really fussy.
There must be someone near you who cannot keep their hands out of raw clay and knows the different types of clay bodies and the basic elements that make up a clay body before adding moisture.
Good luck
Ruth

[Suzan]

Can you be more specific about the problems you are having in drying them? Are they warping, cracking? Why do you keep them sealed in plastic for weeks?

In general, you keep clay objects sealed in plastic only while you intend to continue working on them. When a piece is completed, you may wish to cover it loosely with plastic for a day or two in order to let it dry gradually, to avoid cracking. When it's leather hard, i.e. still has moisture, but it holds it shape without support and won't show a fingerprint or indentation when pressed, it can be dried for a few days with no plastic covering it. Also, the clay mold should be sitting on a piece of newspaper, over whatever surface you're using to move it around (piece of plywood, e.g.), while drying.

Cheers,
Suzan

[rosanna gusler]

buy paper clay from axner or someone like that. it will solve most of your problems. the molds also have less thermal mass. rosanna

[hoknok]

Here are some tips to make your molds dry better.

1. Get the right kind of clay mix. I used to mix my own but its timely so I buy mine from Standard Ceramic Supply Company. Look for clay that is used for high fires. Raku clay can take thermal shock well, stoneware is very durable but not very smooth on the surface unless you get a batch with smaller mesh size of grog.

2. Make sure you wedge the clay well to get all the air bubbles and "floaters" out. Cut it with wire to see if the inside is clean then wedge more. Then slap the clay at an angle downwards towards the table to flatten and thin it out or use a rolling pin. DO NOT GET PLASTER IN YOUR CLAY or it will explode (break) in the kiln firing. If you get plaster on the surface, just scrape it off.

3. I dry my clay on plaster board. It soaks up the moisture well and cover my clay tiles with plastic loosely over the entire piece. I will occasionally lift up the clay off the plaster board and reset it down on a fresh dry board. Just know that clay will shrink as it dries and by lifting it off the surface every while allows for the clay to de-stress and keep from cracking, esp. in the middle.

4. How to cover clay with plastic is important. I will cut a hole in the plastic in the middle or near thicker parts of the clay to allow for them to get more air. The edges will always tend to dry first so I watch them and cover them more closer than I would the middle.

5. You can also place clay slabs, tiles on top of each other and alternate them as they dry to keep from bending and warping. I do the same thing when firing a bisque fire to keep down the warp.

6. Slowly reshape the clays edges and body up until leather hard stage. Once my clay is at leather hard stage, I usually have the plastic very loose on the clay or none.

7. keep the clay away from one-sided air drafts and temps.

8. Remember one thing, you want the clay to dry uniformly. That means the thinner sections get less air and the thicker sections get more.

9. And lastly, you must fast chocolate during the entire drying process so that the great clay elf fiery knows you are serious.

There is a guy on this net named Ted Metz who is a wealth of info. He was my clay/sculpting professor 20 years ago and knows a ton more. He is also very good at metal casting and working. He is still teaching and creating large outdoor sculptures these days.

[Val Eibner]

Generally if you use clay that is intended for sculptural use it will be strong enough and reistant to shrinking to much. I use drywall scraps from building sites to dry most of my clay work onto even my clay molds for glass. I have been a clay artist for more than 30 years and have succeeded in most sizes of work in drying. Don't overdo the plastic stage of covering the work because the plastic does help to slow down the drying but can also keep the clay too wet longer than needed. Proper clay and environment is what is needed. The room temp. dictates the process needed for drying as well as the type of clay used and the size of the mold. I also use dry cleaners plastic that is clingey.
Also, putting the plaster board up on wood slats adds the drying from below. Good luck, V.

[Brian and Jenny Blanthorn]

I've been trying to make some clay molds and I'm having a heck of a time just drying the things.

Typically they are an inch or less thick (some are that thick because I'm intending to use the for low-relief casting).

I'd appreciate advice on drying them -- I keep drying them -- or they sit almost completely sealed in plastic for weeks.

Thanks in advance for any suggestions

- Paul

Use a course clay mix but put china clay slip over top

Do this with slip when clay leather hard

Drying

If bowl keep rim damp with damp rags rags
cover over with loose plastic with hole in centre

U gotta keep am eye on it

Brian

[watershed]

When I was making my hundred pound pieces there would be 3 stages of drying after work was completed.

Tight drycleaner plastic (more porus that trash bags)
Loose dry cleaner plastic
One layer of newspaper over the top (to slow sdown the rim drying)

Greg