Friday, June 20, 2014

Celluclay the Misunderstood

Celluclay is a wonderful product, but it is quite unknown to the world of fine artists, likely because its marketing is aimed at hobbyists and crafters.  Activa, the maker of it, don't seem to know what treasure of versatility and definition they have created, so that would make it difficult for them to promote it that way.  As a career artist who is still very interested and influenced by the craft forms, I was fortunate to have been shown, by fellow passionate creators, the potential of such a unique product that disappointed me at first, and for a long time, since I didn't understand its personality.  Now, I realize how much it has increased the quality of my work.
This article is my way of sharing forward about it.

I also made a video about it. Link is below the article.

I've been told by colleagues that white Celluclay is not as strong as the original grey version.
I've only tried the latter, so I cannot testify for the white.

Celluclay is sold in powder form, in various quantities. I now buy the 5 pound packages.
Maybe someday I'll special order a 24 pound package, since they don't have it in the local stores anymore.  This powder keeps indefinitely on the shelves, as long as it is not contaminated by moisture. Just add water, mix well, and you can have a variety of effects and uses.
Some like to use glue to the mix (and use less water because of that), but I find it is not at all necessary, and it can remove some of the sanding possibilities.

I've been working a lot more with Celluclay in the past two months, both for direct modeling and for casting copies of my works, from silicone molds.  I've learned a lot about how it reacts, and I am sharing here some of my observations.

I would like to recognize here that Ronnie Burkett has been my biggest inspiration to come back to Celluclay, and that without his generous sharing of photographs on his Facebook page, and a few detailed answers to my questions, I would not have even guessed how great a product Celluclay could be.   Look at the work in progress photographs of the puppet heads in his photo album for The Daisy Theater.  Granted, he mixes his Celluclay with Creative Paperclay (about half and half), but that's for texture, and I can tell you it will work without the paperclay.

This stuff seems to have a mind of its own. It can shrink & warp at its own whim.
It can be used for several different applications, but each will require a different approach, and the artist will have to understand  and work WITH IT, instead of frustratingly fighting it.
one who does that will discover a friend and a powerful collaborator, for greater results.
Celluclay is very strong when fully cured, which is why it may be a good idea to trim, cut or carve some thicker parts of it when it it dry, but not yet bone dry.
A fully cured Celluclay cast of one quarter of an inch of thickness will be hard to cut by hand with a craft knife, no matter how razor sharp. Yet it can still be cut with ease on a band saw, behaving much like pine wood.  Still, it will be lighter, so be careful to keep a firm grip on it, and avoid losing control!

While semi-dry celluclay can be re-incorporated into the rest of the batch, I haven't yet tried enough with fully dried Celluclay to be able to tell if it will have the same exact properties as a freshly made batch.  Please share if you have more input!

The mixing method of Celluclay influences its properties a lot more than I ever thought possible.
The written instructions provided with the product are not precise, and don't offer a glimpse of the wonderful possibilities of it for the Fine Artists.

I mix a large ball of Celluclay "powder" in a larger bowl with just enough hot water to moisten everything into a malleable substance, that is still a bit tacky.  Then I sprinkle more powder over the ball, and knead it in, and I repeat until I get the consistency I need for the purpose at hand:

For Casting:
Firm but still slick and tacky enough to be pressed into the mold's details.
I haven't been able yet to get as much detail from a silicone mold with Celluclay as I can with plaster.
I'm working on it, but it may very well be a limitation one has to embrace, instead of being frustrated by. Cracks will likely appear, as they have in my last 3 casts, though eh had been mixed differently. Some are caused by a bad overlap of individual pieces when pressing into the mold, others are from shrinkage. They are easy to patch later, with more Celluclay.

Once the cast has been scooped out and placed back into the oven to dry the inside, there is a strong tendency for the cast to shrink upon itself, especially sideways in the case of a head or mask shape.
Adding a spacer that will keep the sides apart would be advisable, but I have yet to find an ideal choice of material.  So far, a ball of custom-shaped aluminum foil inserted carefully at the opening seems to do the trick, as long as it does not block the heat from entering and leaving.
It needs to stay put, and exert no force outward, or it would warp it that way.

I am working on a method that still uses the freezer to protect the cast as it gets pulled out of the mold,  and yet does not require the use of the oven.  Again, heat increases shrinkage and warping, so if I can be free of that, all the better.  It already works for my approach of paper pulp (made from toilet paper and boiled wheat paste) backed by paper strips, as proven by several masks I've made in the past three years, but I will have to adapt some steps to make it work better with Celluclay and within the small mold opening for my glove puppet heads. 
I will edit this method in here when it is confirmed as viable. Remind me in 6 months, if I have not yet done it, as my work requires me to change main materials depending on the project.
I can only experiment now because it fits within the needs of my current contracts.

For Shaping over an armature or as a surface correcting "clay"
Very firm, clay-like. For this, I keep adding powder until the clay won't accept any more.

This makes a clay that will not shrink as much as it dries, therefore shape and detail is not lost, though it may require refining as an extra step.

Once mixed, Celluclay keeps changing over time, as it evaporates, and as it changes temperature.

Celluclay will get firmer after being in the refrigerator for a few hours. This is great for shaping/modeling over an armature, but not so good for casting into a flexible mold, as the firmer clay resists being pressed into the mold, it tends to lift away from it. It also resists being pushed into details and it does not blend with itself as well.

I tried re-moistening the cold, firmer clay with water to make it malleable again, but it is still not as good as a freshly made batch, still warm from the hot water.
I intend to try to add hot water to the firmed up cold clay, to see if the properties get back to the fresh state.

It tends to droop and stretch, so trying to model a whole ball or block of solid Celluclay can cause a lot of frustration, patience-testing drying times, and a flattened, likely cracked dried sculpture. NEAT! (if that's what you want).  I prefer control, so I follow the example of Ronnie Burkett, and provide a "skull" to the puppet heads I will model in Celluclay.  My choice is compacted aluminum foil, and it usually remains inside the smaller heads permanently.  Often, for rougher, improvised designs, I even shape most of the features with the foil. See an article I wrote about this direct sculpting method.

When my features will be shaped mostly of Celluclay, I mix it firm (as mentioned above), and still try to do it in several steps, drying each before correcting with knives and files, and then adding more.
Again, adding a tiny bit of moisture before adding more wet Celluclay will ensure a proper bond.

Celluclay's natural texture helped match the head with the fabric body.

Celluclay is surprisingly sticky when it is moist enough, so it can grab onto and blend well over various surfaces. For a permanent bond, porous surfaces are better. Paper mache strips and pulp, as a well as unfinished wood,  work very well as substrates for Celluclay.   Most of my paper mache items receive some surface corrections with Celluclay. a slight brushing or rubbing of water mist on the area to be added to, and the Celluclay will stick well. If you forget about the moistening of the surface, you risk a bad bond, lifting edges, or even a separation later, upon impact.


Celluclay needs air to dry. This means that it can take WEEKS to dry when applied thickly in one step.  Who has that long?  Using Celluclay over a temporary form, creating a permanent armature inside, or using it as a casting compound are the best ways I found to prevent interminable drying times.   Add a fan to the drying process, some tiny holes poked into the thicker areas (to be patched later) and smartly applied sessions of heat, and you have a system that is much more reasonable for drying times.

Heat makes paper mache products shrink and warp a lot more, which also increases texture. The price to pay however, is a loss of definition, if one seeks sharp details and sculpted textures.
That's an interesting set of effects to know, if one wants to use them.
To avoid them when they would be unfortunate, here is some advice:
Use fans to dry the paper mache until the whole object feels dry and stable.As mentioned above, poke some holes into the thicker areas. This is also a good way to feel how much moisture remains inside.
Finish with the oven, at low temperatures like 200 - 300F, for short sessions of baking, and longer sessions of leaving the objects in the remaining heat in the closed oven. This will help evacuate trapped moisture

It is a bit difficult and tedious to explain all of it in text, some of it can be quite technical (mold making) and I am still refining my understanding of it, so I'll just link you to the article that he wrote around 1998, which contains the method: Paper Mache Rediscovered

My Celluclay observations shared above can help adjust one's approach to get the best results from this method.  Dare we dream of a Ronnie Burkett video on the subject?  I'll add this for now:

Use a very sharp knife to open a window into the dry-ish clay shell that has been in the oven for an hour (may take longer to reach the stability required).  The dry-ish clay can be remixed with the rest that you will scoop out.  Instead of a spoon which may be too large, use a spatula (clay modeling tool inspired from dental tools) to scoop out the still malleable Celluclay from inside.
As you are scooping, feel the consistency, to avoid scooping out too much. If it happens, put the Celluclay back and smooth with the tool to blend the edges.  Eventually, the semi-dry shell will be felt, and this is where you should stop scooping, unless you want a stronger shell, at which point you'd leave more thickness. Thicker means longer drying times, even in the oven.
At the thinnest safe application, the cast stays in the oven for at least two hours at 200F, and it may require extra drying times above that.  I suspect that after an initial firming up in the oven following the scooping, the cast could be placed in front of a fan to finish drying by air. This would help save energy, and might help prevent some shrinkage. 

Hold the cast with a delicate touch, always aware of how much pressure your fingers apply, to avoid crushing or warping it.

When dry or semi dry, check the cast against a strong light source, to detect weaker spots.
Apply more Celluclay on the outside or inside to strengthen.  This can wait for when the cast is fully dry.


Note the shrinkage compared to the original

The cracks are an interesting effect, if chosen. Easy to fill if not chosen.

The thickness is on average is more or less a quarter inch.
This cast shows no shrinkage, and better detail capture.

Update: CURRENT casting method: I now carefully apply the Celluclay as thick as I need it in the mold, I immediately add 4 layers of paper mache strips in one step, and force it to dry in front of a fan for 12 hours. This provides a stable base, it prevents shrinkage and warping. Then I freeze the whole mold for a few hours, to harden everything temporarily and easily remove the cast from the mold. Some fine parts, like pointy ear tips, can break off, but it is easy to repair right away (even when frozen), with a bit more wheat paste, and smoothing the edges with a modeling tool.  Once out of the mold, the cast is placed in front of the fan again, resting on a grid or over two chopsticks to allow for air circulation below. It should take at least 8 to 12 more hours to dry. 
this approach reduces the shrinkage to such a minimum, it is hard to detect. The previous approach resulted in very visible shrinking, and it was uneven.  In the case of the skull, it made it shrink more horizontally than vertically, making it look skinnier. some of the detail was lost as well.

Celluclay can be left rough, reflecting the tool marks and even featuring the shrinkage on purpose, if one decides to use a very wet mix.

However, it can be made super smooth, with a combination of carving, filing, sanding, and buffing.
To buff, one just needs a bit of water to re-moisten only the surface, and a soft lint-free piece of fabric to rub it until smoother.  For a more shiny, polished stone effect, use a smooth metal tool to buff it.

If it has been re-moistened enough, the surface can be scored to add texture with a dull yet precise hard instrument, like metal modeling tools.

For the dry version of this, a wood burning tool is a powerful detailing and texturing friend. There will be burrs, but they can be carefully sanded off, and a stiff brush will make an easy task of removing the dust crated by that step.  Be careful when applying the sealer over the textured celluclay, so that they won't be filled and hidden by it.

Sealing paper mache of any kind is important for durability, but imperative for performance objects that will be submitted to more abuse by manipulation, transport, and the elements, than the decorative pieces that one leaves on a shelf or protected into a display.  I do the sealing beore the painting step. That way, if my piece gets wet, the paint can be damaged (and repaired later), but the structure will still have been protected.

It is advised to apply sealers in thin applications, each fully dried before the next is applied.
If one used instead a thick application at once, cracking may occur.
It does, in a severe way, with the Bull's Eye, so I use a very soft yet form brush to ensure very thin coverage with nicely blended edges, careful not to leave any quantity that would fill deeper details and later create cracks.  I can speed up the drying of each coat with a hair dryer, and it does not cause cracks as long as the application was thin.

I use the same sealer for Celluclay as I use on the rest of my paper mache.
Currently and for a few years now, I've been using Bull's Eye 1.2.3, by Zinsser, in liquid paint form.
It exists as an aerosol but I have not tried it yet.
It is a stain killer/odor sealer for walls. It resists water and alcohol, despite being waterbased.
It is a perfect ground for acrylic paint, in my experience using many different brands.
It is supposed to be compatible with oil paint as well, but I do not use those over paper mache yet.
I used to use shellac because it is fully natural, but found it difficult to paint over it with acrylics. It is also a brittle finish, and it gets damaged by alcohol, which is unfortunate, since I use rubbing alcohol to clean the inside of my masks.

In my experience, Celluclay is a lot stronger than the usual recycled wood-based paper pulp, yet paper strips are stronger than Celluclay, even at much thinner applications. Strips resist impact and pressure better, so in areas of joining two structures or different materials, and places of high stress, a few strips can be added to land their support. Tips of noses, back of ears benefit a lot from this precaution.

I use boiled wheat paste for almost all my paper mache strip projects, and it is compatible with Celluclay.  I have never had any separation of strips and Celluclay since I've been using this paste.  

The combination of the strength of paper strips, and the stiffness of Celluclay is a stronger and more defined result, which is faster to achieve than a project made entirely of strips.
Still, paper strips deliver a much more lightweight shell, so when comfort and ergonomics are necessary, such as for masks, puppets and other performance props, Strips can be the structure, while Celluclay can be the texture. And this texture need not be everywhere. I really appreciate a contrast of textures on the same project, as it brings more realism to a piece.

I also make my glove puppet necks out of toilet paper rolls made fully rigid by enough layers of paper strips, which also merge that neck perfectly with whatever form of paper mache the head is made of. Celluclay is often used over the paper strip neck, to correct the surface.

I will update this article when I have more insight in Celluclay's properties and usage.
Planned updates:

•Video demonstrating how I mix it.
•More photos:  wet and dry, smooth and textured.

For now, here's a video I made a little while ago, extolling the virtues of Celluclay, and demonstrating how I use  this fantastic product.