Before we can launch into five solid days of natural dye training we need to know what kind of situation we're dealing with. For a dyer that means one thing above all others: what is the water quality? Water can be either acidic or basic. The pH of the water will shift reds either into blue-based reds (closer to purple) or into yellow-based reds (closer to browns).
Dyers also want to know if there are any impurities in the water that will influence the outcome. Iron is a common problem. Look around the landscape - are there red rocks? If so iron oxide may be in the water supply. Are you in a European town where all the local brick is red or pink? If so the red bricks were probably made locally and there may be iron in the water.
A simple pH test strip will give an indication of the hardness or softness of the water. A test batch of dye should give an indication of problematic impurities.
Here Charllotte Kwon washes and scours the wool during the afternoon before the workshop. At our location there were no major issues with the water and we knew what to expect the next day when students arrived.