Paper clay and Cracking - Part 2

"Oh, no. I have a crack in my piece." How often do we mutter this to ourselves. Our adrenaline pours out and our blood pressure mounts!

Back when I was using a regular clay body, any cracks would spell doom (not to mention, heartache) to my piece. Sometimes I can fix the crack if I catch it in time when the clay is still in the leather hard stage or slightly past it. Forget about it if your piece is bone dry. Sometimes you hope for the best through the bisque fire and then hope even more that the glaze will "seal" the crack. Most of often than not, you find it does not work that way.

One big advantage of paper clay over regular clay is that any cracks that develop in your piece can be fixed, even at the bone dry stage. Let me first clarify the different types of cracks and why cracks happen in the first place when making dry to dry joins.

Why cracks happen when joining?

This problem can always be attributed to insufficient moisture in your pieces to be joined using dry to dry joining techniques. Remember bone dry pieces are very, very thirsty and will soak up water very easily and quickly. Beginners usually do not have enough moisture in their pieces to be joined, or your mushy paper clay (which constitute the main "glue" that holds everything together) is not mushy enough (not enough water) or the paper clay slip is too thick (not enough water).

How do you get moisture to the pieces to be joined?

The simplest way is to soak the area in water that needs to be joined. Keep an eye on the part so that it does not revert back to its leather hard stage, or worse still, become mushy and soft. For a piece that is about 1/4" thick, approx. 30 seconds to a minute. I frequently check the water content of the part by taking it out of the water soak and see how fast the water is re-absorbed into the surrounding paper clay. If the water disappears too fast, then I know the piece still needs more moisture and back it goes into the water soak.

If my piece is too large to fit inside a soaking container, I've used wet paper towels pressed against the area to be joined. The dry paper clay will suck readily moisture from the wet paper towels so keep the paper towels wet with a sprayer or a sponge.

Types of cracks.

There are 2 types of cracks. The first kind is the surface crack. This is mostly seen at the very feathered edges of a join caused by the difference in water content between the pieces to be joined and the mushy paper clay/paper clay slip used as "glue." This kind of crack can also happen AT the join. If your dry to dry joining technique is good, this crack can be repaired without any trouble simply by adding more paper clay slip to the crack to "seal" it.

Otherwise, this is a sign of the second kind of crack which is a structural crack. This is no good. Again, the main culprit is insufficient moisture content in the pieces to be joined. Joins like this can easily be pulled apart and will fail very nicely and cleanly. This is a tell tale sign that means your dry pieces need to be soaked longer in water. The thicker the piece, the longer it will take. A lot of it comes from experience working with paper clay.

A good test of your dry to dry joining technique.

• Make a dry to dry join.
• Let it dry completely to bone dry.
• Pull it apart.
• If the pieces come apart cleanly at the join, then you know your joining techniques need more practice.
• If the join holds and your piece breaks away from the join, then you have made a good strong join.

With practice and a good understanding of the physical properties of paper clay, one can begin to understand why one join fails and another survives. Paper clay affords us this training and removes this "fear" element of "Oh, no. I have a crack in my piece." (The above exercise is a good one for beginners to go through. The paper clay can always be recycled)

'Cracks, huh? No problem. I can fix it."

Also see earlier related post on "Paperclay and Cracking."

Paper clay Forever

Unfired paper clay can be recycled indefinitely.

I had some greenware pieces and buckets of dried scraps that had been sitting in my studio for some time.

Working with paper clay, I do not throw away any bits, including trimmings, broken pieces, etc. The cost of paper clay being more expensive than regular clay makes all paper clay artists misers, I think. You can readily make paper clay slip for "gluing" your pieces together from your scraps, use them for surface texture treatments, or reconstitute the dried paper clay back to a workable condition.

I make small scale models of a concept, to see if it will translate well from a 2-D drawing to a 3-D form. This is a great way to anticipate any problems I may encounter before starting on the real thing. All this clay can be recycled so there is no wastage.

The picture shows the way I recycle my paper clay. After slaking for a day or two in a 5-gallon bucket, I mash the paper clay into a thick oatmeal consistency, pour it out on top of bed sheets and let the concrete in my patio soak up the excess water. This may take some time to get the goopy oat-meal like paper clay to a kneadable condition. I knead the paper clay into manageable blocks and I have fresh paper clay ready for use.

Left Over Paperclay Slip? No Problem!

Often times I have left over paperclay slip and if I'm not going to be using it for some time, I dry out the extra moisture and store the paperclay in plastic bags. If I am not in need of fresh paperclay, I may opt to dry out the slip completely (to bone dry), break it up into crumbs and then store it for later use.

The picture shows a batch of paperclay slip that I've poured on to an old bed sheet. I've enlisted the concrete of my patio to help "suck" the excess water from the slip. If you have plaster bats, that will work, too.

My technique take several days and I have to fold/flip the paperclay onto itself many times to facilitate the drying out process. If you are going to be working with moist paperclay, you decide when the paperclay is workable for you. The dried out paperclay can be rehydrated into a workable consistency when the need arises.

Another success with Paperclay

I made this planter for an upcoming planter show at the Irvine Fine Arts Center out of salvaged ordinary clay. A big hairline crack (from the rim to almost the center of the bowl) developed in the bowl section of the planter when I used too much force to try to reshape the bowl. Paperclay slurry and slip was used for the patch.

It went through bisque fire and the Cone 10 reduction firing without any problems. The repair held up nicely. Another piece rescued with the help of paperclay slip.

The glaze is carbon trap shino. The piece was too large to be dipped so the glazed was brushed on. More glaze was hand drizzled on the bottom part of the piece.

The picture shows the completed planter with the succulents in place, ready for the show!

Paperclay slip as SuperGlue

The right ear on this cute little guy broke off after the bisque fire.

The figure was made out of SOBT from Aardvark Clay Company, Santa Ana, Calif. It is one of the basic clay bodies we use at the Irvine Fine Arts Center.

It was reattached using paperclay slip made with paperclay from Laguna Clay Company. The clay is Bmix and sand and paper.

The proud owner of this doggy decided not to use any glaze and opted to fire it (Cone 10 reduction) after the repair, without a re-bisque firing. Approx. size: 6"L x 5"H x 2"D.

Permission granted for the use of this picture of her new pet by Beverly T.  Thanks, Beverly!

Applying Fresh Paperclay onto Bisqued Surfaces.

I decided I wanted this pagoda design on the current sculpture set I'm working on, but the pieces have already been bisqued. The base clay is Bmix and sand, and I've applied a white slip over it in the green stage.

Tracing of pagoda design onto bisqued piece with graphite paper.

Originally, I was thinking of doing a wax resist or a stencil treatment with the design. I opted for the dimensional effect I was able to achieve with my "Take Out Tea" sculpture.

The paperclay slip I use is the Southern Ice Porcelain paperclay. The slip is consistency of heavy cream and blended well to remove lumps. I use a squeeze bottle with a small nozzle - the ones you use to do slip trailing. The design is first transfered on to the bisqued piece and the slip trailing is done free hand. Successive coats are built up to achieve the desired raised effect. Since slip is mostly water, it takes several coats to accomplish this.

What I found is that if my slip is too thick, the edges then to curl and peel from the bisqued surface. Wetting it down with a fine mist from a spray bottle helps. What works better is thinning out the paperclay slip till it's about skim milk consistency and then brushing over the design with a small brush. This thin slip still contains the paper fibers in suspension and this helps to "hold" your relief design in place. Both bisqued piece and the fresh dry slip being very "thirsty" sucks the moisture out of this this watery slip extremely fast. So far, my design has not exhibited curling or peeling at the edges.

After several applications of fresh slip. You can still see the tracing of the pagoda under the slip.

The next stage is to test this application by re-firing the piece at bisque temp and see if this holds.

After the bisque firing,  my added on design held and bonded with the base layer, showing no signs of cracking or lifting off. This is very encouraging! 

After the bisque firing, the graphite tracing burns off. The freshly applied paperclay slip is bonded onto the piece.

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)."

Paperclay and Inclusions - Part 2.

© 2009 by Anthony Foo.

The advantages of Paperclay continues.

In Part 1, I talked about the various organic materials that can be incorporated/kneaded into paperclay to create interesting and random textures. Another advantage of the paper fibers in paperclay is its ability to coat and adhere to various materials that ordinary clay will not. The paper fibers will "grab" on to the irregularities of the surface to be coated and hence form a foundation for the clay to stay on.

In my sculptures, I've used paperclay to coat steel mesh (hardware cloth aka chicken wire), cotton twine, thin reeds, flowers,  twigs. etc. The paperclay I've used is the sculpture body paperclay from Aardvark (IMCO in Sacramento is the manufacturer) and the Southern Ice Porcelain Paperclay, imported from Australia by Laguna Clay Company in Los Angeles. Laguna Clay Company has stopped carrying the Southern Ice Porcelain Paperclay, probably because of its cost.

Both types of paperclay will can be used with the above mentioned materials.  The paperclay slip is made to a "heavy cream" consistency for the brushing method.

When I first start out, I usually brush it on with a soft fan brush, liberally loaded with the paperclay slip. This can be messy work so spread out old newspapers for easy of clean up after. It's slow work here as you need to let the first coat dry completely before the next application. It may not look like much but you are already coating your object with the paper pulp fibers.

I prefer brushing to dipping because I can control the coverage of the details. You may prefer the dipping method if the object to be coated is small enough to fit into your bucket of paperclay slip. Shake off the excess slip and let dry. The first few coats will be slow going until you have built up several coats. From here, it goes pretty fast as the fresh paperclay slip will stick on to the bone dry paperclay coat extremely well. This is actually the fun part and I enjoy this time the most. You can literally see the layers build up.

If you are using the dipping method, it's best at this point to thin out your paperclay slip a bit or else you will have to much slip adhering to your object with each dip. The dipping method is faster but if you are not careful, it will cover up/obliterate the details you have on your object. You can also use a combination of brushing and dipping. Whatever works for you to get to the desired thickness of coverage and still show the details.

In this discussion, I'll use my sculpture "Trapped" to show the different stages in the coating technique. The piece is bisqued fired only. The bamboo reeds and cotton twine burns out; the steel mesh is still encapsulated within the paperclay coating.

The sculpture could probably go to Cone 3 or 5 with the steel wire embedded in it, but since I'm using a community kiln, I'd rather not risk damaging the kiln. 

Initial forming stage - Materials used here are chicken wire, bamboo reeds, cotton twine.

After first coat of paperclay slip, brush technique, drying in the sun.

After 2nd day of coating. There must have been approx. 15 coats already here. I lost count!

Final stage. I'm happy with the coverage and thickness of the paperclay slip over the entire structure. The build up of coverage is anywhere from 3/16" to 1/4" thick.

Ikebana, Ceramics & Swordsmanship

I recently completed a short 5 session class in the Sogetsu style of Ikebana (Japanese flower arrangement) at the Irvine Fine Arts Center conducted by Takeichi Haruko Sensei. This picture was taken in class (2nd week) after we completed the arrangement, but before the Sensei came around (with her clippers in hand!).

I enjoyed the class tremendously. The 5 weeks went by so quickly. The ceramic vase I made fitted the style of the arrangement so I used it. It's a high fire Kazegama style firing (ash firing), invented by Steve Davis of Aardvark. The vase is about 12" high, made out of paperclay, flashing slip was applied to the surface of the piece in the greenware stage. The texture you see is actually left over dried paperclay that is "glued" to the vase with paperclay slip. The texture and colors came out beautifully in this piece.

One thing that struck me were the quotes Takeichi Sensei shared with us. Even though it came from the Ikebana perspective, with my training in Japanese swordsmanship I now better understand  what my sword Sensei (Katsuse Sensei) was trying to tell me. My two favorite quotes from Takeichi Sensei:

1. When a man cuts the pine tree, it is no longer a pine tree. It has become the man.

2. Even if you are a beginner in Ikebana, and you have a small vase, make your arrangement big. Do not let the size of the vase limit you.

Hearing those words for the first time I smiled inside and I thank Katsuse Sensei, "Now, I'm beginning to understand a little bit."

It is incredible the feeling you get when you view these flowers and arrangement in your home. The spirit from these humble flowers that so many of us take for granted fills one's heart and definitely fills the room.