- Fri Mar 02, 2018 4:46 am
First of all, I want to commend you and your Boyfriend for the inspiration for this project.
I've explored this myself, I even made a prototype drumshell from sawdust, and I can share a few realizations. I list a few binders below.
Experimenting will be necessary. Testing various recipes and methods etc. This can be fun, if you see it as a challenge.
I used sawdust, water and acacia gum. I made a kind of dough, or clay, out of it, and shaped it onto a cylindrical mould.
It started sagging down before it dried, so I wrapped it in cheesecloth to keep it in shape. Not very elegant, but it worked. The cheesecloth is now part of the exterior, and it looks cool with the sawdust, a kind of natural art.
Very little gum powder was required, diluted with lots of water. The trick is not to overwet the sawdust. Just enough to make it stick together and form a "dough", but not so much that it sags while drying. I added too much, lesson learned. It would help to add fibers to give it strength, like hemp, jute, etc. Anything really, even strips of cloth, or long flax-like grasses like sawgrass, or bark from canes, weeds etc. The prototype is very strong, but on a full sized djembe, if it gets dropped, I'm afraid sawdust doesn't have long enough fibers to prevent a piece breaking off the foot or stem. It won't crack though, which is one advantage over wood.
Here's a few ideas for binders, I can provide more if required.
A) Protein Resin: Essentially it's Protein powder + Strong Alkali/base + water. Very strong. Protein isn't cheap though.
B) Acacia Gum aka Gum Arabic: Not cheap either, but you can dilute it a lot and it still works, and it might be more available locally, since it comes from Africa. I think mine came from Senegal)
C)Tannins. I was able to make a composite with hemp fibers and tannin from treebark. Too much and it becomes soft, the key is to add enough to make it stick, but not so much that it's soft. Abundant, cheap, but requires experimenting.
D) Alkali. Simply mix water with alkali and sawdust and allow to dry. Might not be strong enough, but it's the basic principal behind paper I believe. (Alkali dissolves the surface cellulose, so as it dries, it should form a bond)
A: "Soy/Protein Resin": You can make a glue from any protein powder (soy, gluten, etc.) combined with a strong Alkali such as Lye(Sodium Hydroxide, NaOH), or Potash (Potassium Hydroxide, KOH). Potash is easier to obtain, because you can make it from wood ashes. Simply dissolve ashes in water, filter, and allow to dry. I buy it from a soap making supply company.
This is how Soy resin is made, and it is a very hard, strong substance. A small amount, dissolved in water, mixed with sawdust, and allowed to dry, would form a good bond. The Alkali will partially dissolve the cellulose in the sawdust, and make it bond, and also the water will cause the cellulose to bond naturally via Hydrolysis, which is how paper is made.
You might even be able to use Alkali and water without protein, experimenting is recommended.
But be careful! Alkali can burn skin, and spatter when mixed with water, so read the instructions, and use Ph strips to measure the alkalinity (cheap, available from home brewing supplies)
B: Acacia Gum, or Gum Arabic. This is a sap from an Acacia species. It's renewable, but not the cheapest option. However, only a small amount is needed, so it can be very dilute, to make a strong composite with sawdust.
C: Tannins (natural, plant based chemical) This is perhaps the cheapest option, as you can literally make it from waste materials, such as bark, leaves, etc, by soaking in water, or boiling. It's basically the same idea as dying cloth, except you are dying the sawdust, and as it dries, the dye helps the sawdust stick together. You may find certain chemicals make it work better, like citric acid, or acetic acid (vinegar), or even minerals, like"tea" made from metal-rich clay(red clay, or dark mud), there's chemistry involved. I learned about this from Bogolanfini, the mudcloth technique, and it uses plant tannins, mud, and binds to cellulose (fabric).
D: Alkali is basically explained above. Use caution. (always add alkali to water, not water to alkali, or it can spatter. Always wear eye protection and gloves. Never get it wet or can "explode", causing caustic burns) Could be very useful if it works, since you can make it from the sawdust by burning it. To burn sawdust, first wet it, form into logs or bricks, pressing firmly, allow to dry, (hydrolysis should make the cellulose stick to itself) then burn as usual in a fireplace.
Also about Water Based vs Epoxy:
Water based binders work best because as the water dries (evaporates) it leaves behind air gaps, which means the final product doesn't have to be so heavy. Composites made from epoxy resin and chip materials tend to be heavier than the Djembe hardwoods. Also they are not environmentally friendly, so defeats the purpose. Although if plant resins are used, it can be clean. In this case, plant sap (the sticky kind which leaves resin) can be mixed with sawdust and then allowed to dry. Heat will be needed to speed the drying process.
It can also help to make the composite two stages.
First, binding the sawdust or fibers with a water based binder.
Then when it's dry, applying a water-resistant chemical, like shea butter or oil, beeswax, or tree resin.
This way, you get the ease of working with water-based chemicals, and the added strength from the addition of water repellant chemicals. Again, experimenting is required to find the right combination.