Textures, Textures, Textures

Slab built Grogzilla® sculpture clay and paper clay.

Grogzilla® clay is a highly grogged sculpture clay with feldspar crystals. At Cone 10, the feldspar crystals "pop" and you get random white crystals.

Flashing slip on greenware. Carbon trap shino glaze on bisque. Fired to Cone 10 reduction.

They are totally functional pieces, yet very sculptural. I really like the textures and warm earth colors.

Each approx. 12"H.

Sometimes I Do Make Functional Stuff ...

A tall, slab built triangular Ikebana vase. High fire Cone 10 reduction. With green to black flashing slip on greenware. Carbon trap shino on the bisque.

18"H x 7"W x 7"D. I made the piece hefty and heavy to be able to take some large sized branches for an Ikebana arrangement.

I like the sculptural element of the piece. It can stand alone as a sculpture and it also works beautifully as a functional vessel. I think it would look great with some cherry blossoms branches.

Structural Support Considerations

Whenever I build my pod shaped vessels, I have to think about how to fire them in the kiln for bisque fire and at higher cones, for example at cone 5 or cone 10.

In this piece, I wanted to use the Van Gilden’s flashing slip which cracks really nicely at Cone 10 so I had to design a structural support system that will be strong enough to survive a Cone 10 fire.

The donut ring and supporting tubes were all assembled from bone dry paper clay pieces using dry to dry techniques (top picture).  

As my pod is rather heavy and tall (36” high), my support has to be well constructed to withstand any movement in the kiln during firing. The legs were thick slabs rolled into tubes.

Lateral struts at the bottom were added to give sideways rigidity.

This is structural support for my pod which can be seen in the background. The Van Gilden's flashing slip has been applied to it. It's bone dry and it's ready for bisque firing.

 In a way, the structural support is like a piece of sculpture in itself. I plan to reuse this support for future works.

Paper clay And Structural Support

Case Study: "Within Us"

This is the completed piece. It is mounted with a stainless steel pin into a solid textured aluminum block.

The issue arises when it comes time to fire the piece, first in the bisque fire and then to Cone 10 reduction. Due to the shape of this piece, I knew I had to create some kind of a support or scaffolding to prop up the piece during the firing process, and one that is strong enough to withstand a high fire at Cone 10.

The scaffolding was made from paper clay with a combination of dry-to-dry and leather hard-to-dry joining techniques.

Creating a piece is one thing, completing it is another. In a piece like this where there is no stable base for the piece to rest on, I had to devise something. Paper clay allows me to easily "engineer" this support to accomplish this end.

For the story behind this piece, click on this link.

This piece is in a private collection in Orange County, CA.

Grogzilla, Godzilla, Moxilla, etc

I found out about this high-grogged NON-paperclay called Grogzilla™ when I attended my first paperclay workshop with Graham Hay in Santa Clara at Clay Planet back in 2007. It is manufactured by Clay Planet and is rated to Cone 10.

What attracted me to this "traditional/regular" clay was its rough texture and the little bits of "white godzilla teeth." That was my first impression of the feldspar crystals that popped from its surface. (See close up shot below) It does look like little dinosaur teeth so I thought the name was quite appropriate.

This hand-pinched bowl was fired in Steve Davis' kazegama ash kiln at Aardvark. I applied a thin layer of flashing slip on the top 1/3 of the bowl. The rest of the bowl was left bare. You can see the ash glaze over the flashing slip as a slight grayish brown coating. At high temperatures in the kiln, the feldspar crystals in the clay break through the surface and melt into little white globules.

I enjoy this texture very much and have been using this clay in my "sandwich" technique. (See earlier post). Paperclay allows me to incorporate this "regular" clay into my paperclay sculptures.

Paperclay & Shrinkage

One of the things I get asked with paperclay is "How much does it shrink?" That is a valid question and after all, it's good to know all the technical details of the clay when one is working with it.

The paperclay and subsequent technical infomation provided here is manufactured by IMCO in Sacramento. It's a proprietary blend and is carried locally here in So. Calif by Aardvark Clay Company in Santa Ana, in 25lbs bag.

The information provided here is from my own experience.

From green to bone dry - 5 %

After bisque - not measured

After high fire (Cone 10 reduction) - 10%

Total shrinkage is around 15%

Considering other traditional clay bodies (total shrinkage ) is anywhere from 8% (low end) to 12-13%(high end), this paperclay shrinkage is quite a bit. It's good to know so you can compensate by making your pieces a bit larger than you normally would.

Paperclay and Cracking

© 2009 Anthony Foo.

The bane of all ceramic artists - CRACKING! There are many reasons why and when a piece cracks.

1. Crack during the drying stage - greenware

2. Crack after the bisque stage

3. Crack after the high fire (in this case, Cone 10) stage

What to do and how to mitigate the problem. The discussion here pertains only to paperclay, and is based on my personal experiences with the sculpture paperclay from Aardvark Clay Company, Santa Ana. IMCO (from Sacramento) is the manufacturer. I've been using this paperclay since 2004.

1. Crack during drying stage - from leather hard to bone dry greenware.

This is usually due to improper/weak joining, especially when you are doing dry to dry joints. Another reason is unbalanced/uneven drying once the joints are formed. There are 2 kinds of cracks here.

One is a surface crack formed primarily from not using enough moisture in your paperclay slips/slurry. The solution here is to use a thinner paperclay slip (ie more watery slip)  and cover/re-coat the cracks. It may take several applications to completely cover the cracks.

The other more serious one is the deep structural crack due to improper technique. I find that the only way to find out if this is a structural crack is to take a knife or similar tool and dig out the crack and see how deep it goes into your piece. If it is not too deep, the good news is that it can be fixed with paperclay. Remove enough of the dry paperclay until you do not see the crack. Make the hole/opening large enough to do a decent repair/patch job. If during this digging out of the crack, your piece/seam falls apart, then you really know you've not done a good joint. Don't worry. Don't panic. Just start over and this time make sure you spend the time making a good, strong joint with good technique. That's one of the advantage of paperclay. You just can't go wrong with it, and even if you did, it's fixable. This advantage alone gives me peace of mind.

Do not be stingy in your "excavation." Spritz the area well or soak the area with a wet paper towel and let stand for some time for the surrounding dry paperclay to soak up this moisture to create a better moisture balance. Use very "mushy" paperclay to fill in the hole you made. Keep the area moist as the surrounding dry paperclay will want to "suck" the moisture from this spot, so keep the water sprayer handy.

2. Crack after the bisque stage.

Sometimes, even with our best care and technique, we still get cracks in our pieces. Sometimes everything looks good in the green stage, but after the bisque fire, you notice the cracks. If it is a hairline crack, it's really tough to do anything about it. If the crack is large/wide enough to patch with paperclay slip, you may try that. I ususally use a very runny paperclay slip as filler. The bisque piece will absorb the water from the paperclay slip very quickly. Several coats may be necessary to fill the crack. It also depends on how bad/serious the crack is. To be sure my patch holds, I usually re-bisque the piece to test my mending. If it survives, it stands a good chance in the high fire; if not, it's better to remake your piece.

3. Crack after high fire.

This happens sometimes as high fire (Cone 10) puts a lot of strain/stress on a piece, especially tall, vertical pieces.  As sculptural pieces, there is no reason to take it to Cone 10. A Cone 6 firing will do fine. When you find a crack in your piece after a high fire, it's pretty much "putty/epoxy time." Unless your piece is meant to hold water (for example, an ikebana vase or something similar) I usually don't do much about it. Sometimes the crack adds character to the piece, sometimes it does not. At this point, you can't do much fixing it.

A very appropriate quote from my instructor, Julia Klemek, "Don't fall in love with your piece until it comes out of the kiln (this is Cone 10 fire)."