How to make and work with cellulose cement
Key elemsnt of sculpting with cellulsoe cement:
1. Armature: The first thing to do is to build an armature of the object you want to make. An armature can be built out of just about anything but it must be rigid as the cured material can crack if the armature flexes especially where the layers of material are thin. Thicker material weighs more but is structurally quite strong so decisions have to be made at the outset about strength vs weight. This medium can be readily be spread over a foam core as well as steel wire mesh on a steel frame for larger, more open works. However this material used far less bird wire mesh (two layers is usually enough) than would ferro-cement where at least 5 layers of mesh are required to prevent the render/plaster from slumping through. Although I tend to use mild steel reinforcing as my base frame. Wood is just as good and styrofoam also makes a good armature as this material readily sticks to it.
See below for an example of an armature on a steel frame
2. Preparation. Once the armature is ready then the next step is to produce the material. Taking ordinary newspaper (glossy paper, cardboard, egg boxes etc are not at all suitable so do not use them). Tear the newspaper into one to 1.25 inch (25 mm to 35 mm) strips. Remember newsprint has a definite grain and tearing along the grain is quicker and easier than trying to tear across the grain. Place these strips into a bucket, or mixing container (I use 20 - 25 litre (4-5 gallon) paint buckets made out of metal or hard plastic. When it is about a third full add water to cover the paper. The amount of water to paper is not critical but too much takes longer to break the paper down. Too little and it becomes difficult to mix properly but a rough guide would be 40% paper 60 % water. Let the paper soak overnight (or for about a minimum of 3 hours ) before advancing to the next step.
Taking an electric drill with a paint stirrer ( as per the illustration above right) tightly fixed in the drill chuck, mix up the paper until it is a fine slurry with no discernable bits of paper present. I have noted over the years when the mix when the grey mixture starts taking on a lighter hue then the slurry is properly mixed. If the paper has been soaked for sufficient time, this process should take about 2 minutes. Now it is time to drain the water out of the slurry. I use a piece of old hessian for this and pour the mix into that and lightly press out the excess water. I then store this material in a plastic container which has a sealed lid. Add some bleach (there should be a slight but not strong smell of bleach in the container) and thoroughly mix that into the moist mix to prevent it from getting mouldy while it is stored. The bleach also cuts down any risk of mould erupting when the paper is mixed in with the cement. The moist mix can be stored for months this way and if it starts drying out a bit more water added to keep it usable.
3. The ingredients:
a. Cement - I find off-white (ivory) cement gives the best results as it has a versatile natural colour when cured and sanded that can either be left in its bone-like colour and sealed with a clear concrete sealer or painted and stained to suit the projects needs. It is essential to only use cement without any lumps or hard bits that is often found even in brand-new unopened pockets of cement when these are kept in humid areas. If there are any lumps present when the bag is opened it needs to be sieved before use. I keep the cement in a plastic storage bin with a sealable lid to keep the cement as fresh as possible
b. Bondcrete - I tend to buy 4 litres of this as it is much cheaper in bulk.
c. Paper. The mixed mashed and drained paper (remember it must always be mixed with bleach before using to prevent it being attacked by mould at any point)
d. Raw linseed oil can be added in moderation (2-5% or so by volume) to increase plasticity and workability of the material but this is not essential.
The cement and the paper fibre mix are mixed in on a 1 to 1 ratio by volume. I use a plastic bowl of a known volume (left in the paper wet mix storage bin) in and another same sized measure in the cement storage bin. Having a measure of a known volume makes it easy to measure off the next part of the mix cement conditioner/ plasticiser (normally Bondcrete) . Mix in 10% to.15% of Bondcrete by volume to the paper mash making sure that it is thoroughly mixed in. Then add in the cement in an equivalent volume to the original mashed paper in the mix. Mix this in thoroughly until you get a texture that is similar in consistency to a wettish potters clay. It must not be too thin as it will tend to slump when applied and not too stiff as that will go off very quickly. The mix can be varied according to what it is being used for. Fom moulding one might make it a bit thinner and for modeling a bit thicker. Shrinkage is not a great issue with this material but there is some. Gebnerally the dryer the mix the less the shrinkage. I prefer to use off-white or ivory cement as it gives a better range of options for the finish but ordinary grey cement is just as good. It is really a personal preference.
5. Applying the material. When I am ready to lay the material onto the armature I mix up as much as I will be able to use on in about a half an hour as after that the mixtures starts going off. Once its starts going off it can still be used by adding a bit of water but if there is any material left over it must be discarded. DO NOT put this mixed material back into the storage bin. The first layer of the material needs to be a very thin one, especially when it is applied over mesh. Too thick and the weight of the wet material will cause the material to slump off the armature. This is then left at least overnight to dry. Lightly wet the first layer with water from a spray bottle and apply the next coat. The second layer is used to rough out the final shape but I suggest that one resists trying to get too close to the final shape yet. All of my students have tried to work with this material as if it were clay. It is not and one should take that into consideration. I tend to leave of the detail until the very last layer.
At any point the material can be ground off or shaped with an angle grinder using a ZEC disc or very course sanding disc say about 18 grit. It can be drilled to add in other elements or as a support for any changed shape that you might decide to as you proceed with the work. It can be carved but grinding shapes into the surface gives a better result.
6. Finishing. This material is very versatile. It can be finished to just about any surface a creative mind might want to come up with. What it needs however is to be sealed against the incursion of moisture. One can use normal house paint (interior or exterior PVA ) or a clear sealer like those used on concrete driveways, or a host of other surface treatments including covering it with a thin skin of fibreglass. any surface in contact with the ground should be sealed witha bitumen based sealer.
A wander though theh works shown under Cellulose Cement will give you some idea of what is possible. But these finishes are no limit on what a creative mind might be able to achieve with this material.
Here is how the above armaure turned out when the work was completed and left in its natural colour. It was sealed withseveral coats of a clear concrete sealant