Updated: Oct 14, 2020
When going on holiday you check the doors are locked, and the socket for the kettle, is off.... well maybe some of you do.... I ALWAYS DO!! :-)
The same notion of paranoia is also true for when using synthetic or natural dyes in your dye bath...well you don't need to check the power, but you do need to check the pH. The pH is a scale used in chemistry to specify the acidity or basidity (level of alkalinity) of an aqueous solution. Acidic solutions are measured to have low pH values, neutral falls in the middle of the range at around pH 7, and basic or alkaline pH's have the higher values from 8 through to 14. Chemically the pH scale is logarithmic and inversely indications the concentrations of hydrogen ions in the solution.
Why is all this important? Well the fact is natural dyeing is in essence a chemical reaction in your dye pot, so you must ensure the chemistry is right for everything to work as it should. Many dyes are termed reactive, or need oxygen reduction, so are reliant on the correct chemical conditions so checking the pH is critical. For example when using indigo, it is essential to check the pH for optimal dyeing performance. such that it is around pH 10-11 at the time of setting up the vat. This is required to liberate the indigotin from the dye. However high pH can damage wool and silk, so some adjustments will likely need to be made to the vat to create the optimal pH depending on what type of fabric or fibre you are dyeing. As a guide pH levels are recommended as follows for indigo to work without damaging your fibre:
for wool adjust the vat to aim for a pH of 9.0 to 9.5
for silk adjust the vat to aim for a pH of 10.0 to 11.0
for cotton or cellulose based fibres adjust the vat to aim for a pH of 11.0 to 11.5
Likewise when using procion MX dyes for cotton, or acid milling dyes for wool and silk, testing the pH is essential to make sure the dyes work most effectively. For Procion MX, the conditions need to alkaline so soda ash is used to raise the pH, and for acid milling dyes acidic conditions are required, so the pH is adjusted with citric acid (or vinegar - acetic acid) to get the conditions right to fix the dye properly in the dye bath.
As a guide the pH scale is interpreted as follows:
pH 1-3 - is a highly acidic substance (required for acid milling dyes, and sometimes to liberate natural dye stuffs.
pH 4-6 - this indicates an acidic substance.
pH 7 - this is a neutral pH as is best for when washing wool and silk, and also neutralising either acid or base (alkaline pH), and after dyeing with indigo to neutralise the alkalinity and help fix the dye into the fabric or fibre.
pH 8 -11 - this is an alkaline pH. This pH is best for when using procion MX dyes when dyeing cellulosic materials such as cotton, rayon and bamboo. It is also the optimal pH for when using an indigo dye vat, where an alkaline pH is required to fully liberate indigotin. Always take care at this pH range when dyeing wool, as alkaline conditions have the tendency to denature protein based fibres like wool, so it is recommended to keep closer to pH 9-to 9.5 when dyeing wool with indigo.
pH 12-15 - this range is highly alkaline, and is usually best avoided - only concentrated alkaline scouring washes for cotton or other soda-ash based products should reach this pH level.
Here at Wonky Weaver, we offer three different products for checking the pH including a handy pack of paper pH testing (litmus) paper which includes the full pH colour chart. The pH strips can be torn off and used to do the pH check. In each pack there is 80 tear off litmus pH test strips. We also have a pH testing reel, which contains 5 metres of pH testing paper which can be conveniently torn off as needed, whilst protecting the rest of the paper from contamination as it is held in a little plastic reel container. The third and more advanced product or testing pH is our snazzy little digital pocket pH reader which has a greater accuracy than the paper, and is a stylish little add-on to your dye studio.
Whichever pH testing method you choose, they all work well, but most importantly the message here is to check the pH of your dye baths, and always wear gloves and protect the skin when handling any liquids or reagents at both the acid or alkaline extremes of the pH range.
Have fun, and keep being creative with natural colours!