Waterproofing
Various materials have been waterproofed around the world over the years. While there are some incredible modern high-tech impregnation products, I’ve had a couple of times when I’d like to apply the old-school natural compounds. I know that the waterproofing won’t last as long or perform as well as a hydrophobic spray, but the look and feel of a waxed surface can’t be replicated any other way.
Recipe
There are several variations of components and mix ratios out there, but I’m sticking to an old and proven one:
2 units beeswax (by weight)
1 unit boiled linseed oil
1 unit boiled turpentine
Linseed oil is a drying oil so that it will oxidise and stiffen over time. Turpentine is added to dilute the linseed oil and slow the curing process, allowing it to penetrate the item to be waterproofed. Beeswax is the leading waterproofing agent. Care needs to be taken with linseed oil, as it generates heat during curing, and there are many known cases of linseed oil-drenched rags catching fire when crushed together and left aside. The correct method is to spread rags out on a non-combustible surface until they are dry. I’ll be using a brush to apply my solution, so I am not particularly worried about spontaneous combustion, but I’ll still put that brush outside to dry.
Heating and mixing
I’m using a double boiler (bain-marie) to heat my solution. That means I’ve got a pot filled with water on the heat source, and my mixture is in another pot (or a mason jar, in this case) that is heated indirectly. This is to avoid overheating and minimise the risk of fire, as all components have very low flash points.
After waiting a long time for my improvised double-boiler (with an inverted saucer between the two pots to prevent overheating) to reach the correct temperature, I opted to switch approaches. Beeswax will melt at around 65°C but can burn (turn brownish) over 80°C, so I got out my trusty sous vide circulator and set it to 70°C. This not only lets the water heat up much more quickly and start the wax melting in the inner pot, but also prevents any potential burning.
Application
While it was still hot, I applied the mixture to 2 small cotton pouches, a supermarket cotton carry bag, and the jute canvas from a coffee bag. I used a brush to get the liquid applied in a thicker layer. After it cools, the application needs to be done with a cloth. The items were treated with a hairdryer to melt the surface wax into the material, and then went outside to cure for at least a day. Considering the amount of volatile compounds in the mix, they might have to stay outside even longer than that.