Stone washing got its name from tumbling garments with large stones. Several folks have claimed to have invented it, but it first shows up about in the 50’s. Originally pumice stones were preferred because lava does a great job of fraying threads. But it can be done with a concrete mixer and large granite stones. This will soften the fabric and add a little dirt in the seams but does not generally fade the cloth.
Sandpaper can be used to abase fibers and threads as well. This gives more control on the distressing but is labor and time intensive. All different kinds of sanding tools can be used, but with some a touch with skin is all that’s needed for a bloody abrasion. Gloves and masks are mandatory. Sand blasting works unbelievably well, but needs air power and other equipment.
Chemical stone washing began with spraying bleach on jeans and laying them out in the sun. Or that’s one version. Now a wide variety of chemicals are used to achieve an equally wide variety of results. TSP is an alkaline that effectively makes fabric look like it’s been washed 20 times. Bleach is the most common chemical used for removing color, but not the only one. Potassium Permanganate is another potential bleaching agent.
When one talks about the acid washed effect, it usually refers to pumice tumbling and chlorine bleach until the fabric is almost white. Muriatic acid is another common chemical used to break down fibers.
We are technically using a cellulase enzyme to decompose the cellulose fibers of the threads. Picking the right enzyme for the fabric is key. The one we’re using will only work on cotton, for instance. Since the enzymes are actually breaking down the fabric, the frayed treads appear. It will also cause dye to be released. For a greater effect, extend the agitation cycle. Our particular enzyme is best with a ph of 6.5 set by using a buffer and a temperature of around 115 degrees. They say to use half a pound of enzyme for every hundred pounds of clothes and run for 30 minutes. Those are the manufactures directions, but experimentation pays benefits.
A way to soften clothes without distress is to use fabric softener. We are going to use a silica based softener that suggests a ph of 5.0 or lower, temp of about 115, 2 pls of softer to 100 pounds of clothes. You can also use off the shelf fabric softer, but the recipe will have to be gained by experimentation.
Chemically specking, we have a choice of acid or base to play with. A basic rule of thumb is a base is less aggressive, but for every rule there is an exception. We have ph adjusters, which is just a basic acid and alkaline. In our class, Phosphoric acid and Potassium Hydroxide. I am not a chemist and I do every bit of research I can think of before I start adding chemicals. You are responsible for what you mix. An actual acid or alkaline bath must be neutralized once the effect is achieved, otherwise the process will continue. Even so, the process weakens all threads and being aggressive can lead to seams failing and pockets falling off.
The chemicals we are using are chosen because they are very friendly to the world. In general, whatever ph is needed for the treatment, it should be neutralized for disposal. The key is just because you have a neutral ph does not mean you have an inert chemical. I cannot cover all the possibilities in a class, but research can narrow the chance of harm.