Period Recipe: This recipe is an approximation, since the original recipe specified “litharge,” or lead monoxide (PbO) which is extremely poisonous.
Bright Idea: Leave out the lampblack, and you have a recipe for a nice civilian waterproof cloth.
I strongly recommend this recipe because it is about as authentic as you can get without putting life and limb in danger.
- Boiled linseed oil
- Mineral spirits paint thinner (or turpentine)
- Lampblack (comes in tubes or dry powder)
- Japan dryer
- Corn starch
- Make a sizing by boiling about a quart of water and adding cornstarch mixed in cold water until the mixture becomes a little syrupy.
- Paint the cloth with the cornstarch sizing and let dry.
- Mix one part of boiled linseed oil with one part of mineral spirits. Add lamp black until the paint is a very opaque black. Add one oz. (2 tbsp) of Japan dryer per pint.
- With a brush, paint the cloth with the blackened linseed oil and let dry. This can take several days.
- Mix one part of boiled linseed oil with two parts of mineral spirits. Add one oz. of Japan dryer per pint.
- With a brush, paint the cloth with the clear linseed oil mixture and let it dry. This can also take several days. Two coats of this mixture should give the results you want. (You can omit the cornstarch sizing if you want, but the oil-based paint will pretty much soak the cloth.)
For best results let the cloth cure for 2 weeks hanging outdoors.