We use pH Indicator Strips to measure the pH of an indigo vat. In other words, they help us determine if we need more alkali or acid to balance the vat. We also use pH strips with other dyes to measure the pH of the dyebath.
These are extremely useful tools to quickly check your indigo vat or to determine the pH of your water supply. Natural dyes colors may be shifted by adjusting the pH of the dye bath. Therefore, our pH strips come in handy when deciding on increasing or decreasing pH.
How to check pH
A common question I get about checking indigo or highly colored dye baths is: how can you possibly check pH when the indigo vat is dark blue and immediately stains the pH paper so it’s unreadable?
For natural dye baths
Light colored dye baths are relatively simple. Quickly dip the pH strip so all 4 boxes are immersed in the liquid and read the pH results.
Dark or very highly colored dye baths like a strong cochineal bath, or an iron-rich bath will discolor the pH strip, making it difficult to read. In this case, dip the very tip of the strip into the vat, as below. Since these baths are often acidic, pay special attention to the very first square. This is the one that indicates acidic or lower pH. That square will become pinker as the ph goes lower.
For indigo vats
The trick is to have the vat surface very still. Dip only the very tip of the strip into the vat, not the entire strip. The bottom square will be discolored by the blue pigment in the vat, but hold the strip steady in the liquid. Don’t dunk it. And watch the liquid from the vat travel up the connected squares. Soon you will see the third square from the bottom change from yellow to orange. It might change nearly to red in the alkaline liquid. Reading the legend, you will see that if the third square from the bottom is orange red, the pH is about 10. The redder that square gets, the higher the pH.
Check out the “What is pH?” link for a more detailed description of pH and why it is important.
- We package our pH Indicator Strips in sets of 50 tests with a full color indicator chart and instructions for use.