For the control of the Commons project we have built a vessel from an old fishing Zille and a windsurfer, added a mast and a junk rigged sail made from locally produced cotton canvas. Yes, the cotton is not locally grown, but the fabric is locally manufactured. We have tested the sail and it works more or less (we need to do some adjustments to get the tension sorted out). But we have already seen the arrival of that great enemy of natural fibre cloth, mildew. Some dew over night, some rain, damp cloth and the sail is turned into food for the mildew spores.
The classical way of getting rid of this is tanbarking, the process of tanning the fabric, originally with bark. According to some posts in the wooden boat forum, the best bark to use is the tree from which Betelnut is taken. This red nut is chewed all over Asia as an easily reached alternative to smoking I guess. The wilderness rocks and streets of New Guineau are covered in red spit, girls in miniskirts sell it at traffic lights and from little glass booths on the outskirts of Tainan in southern Taiwan. The tanning process is caused by the tannins in the bark, the colour is probably related to the redness of the nuts and the resulting (and almost revolting) spit.
Following the inevitable logic of recycling, upcycling and seeing what is available that we have around here, we looked and saw a vast quantity of coffee being drunk. Which apparently has enough tannin, as does tea, to keep your teeth coloured. Red wine is good too. So this morning a visit to a local coffee shop left us with a small rubbish bin filled with several days espresso coffee remnants, fair traded coffee from India, Africa, Middle and South America. It has done its duty as a stimulant for drinking, now it makes a stop between the machine and the compost heap by being cooked to remove as much of the tannins as possible. Apparently, however, the tannins in coffee are only pseudotannins. So I suppose we will find out whether or not they have any cloth preserving properties. The smell of over boiled coffee is slowly getting irritating, or am I simply overstimulated from caffeine aerosols?
At home I will dive into Tom Cinliffe’s “Hand Reef and Steer” (anybody who can explain that title is most welcome to illuminate me!) which apparently has a good recipe for sail tanning. It seems that alcohol and acetone are used in tanbarking to extract the tannins, as they are not readily water soluble. As we are using pseudotannins we can leave that part out. I am trying to determine the functional properties of urea in the mix (I think pissing on the sails is a bit rank) and to see what other parts of the potion are useful. There seems to be a second phase of fixing the tanning (also called setting a dye using a mordant), which apparently can use bichromate (a pound to 4 gallons is 36 grams per litre) but this seems to be a nastily toxic, carcinogenic chemical that we should keep clear of. Plus it is usually acidic, so needs to be mixed with Sodium Carbonate (washing soda) to raise the pH until it is no longer liable to eat up the fabric instead of protecting it. This seems all a bit messy!
We might have to stick with nonfixing or finding some less toxic fixing techniques. Looking at people dying clothing with coffee, we find that alum, vinegar and soda ash can all be used as mordants. I will see what the local chemist can offer us.
Tomorrow I will update this post with details as to what happened, including a hopefully well coloured photo.