Soda ash (sodium carbonate, or pH Up) is most easily
dissolved in water that is at a temperature of 95.7 degrees Fahrenheit
(35.4 degrees Celsius). It is less soluble at higher OR
Dyeing with Procion MX dyes is best done somewhere between 35 and 45
degrees Celsius, or 95 to 113 degrees Fahrenheit. Other
"cold water" fiber reactive dyes such as Cibacron F and Drimarene K prefer
temperatures that are only slightly warmer. At temperatures
significantly above that range, the dye will react very quickly with the water,
leaving no dye to react with your fiber. If you heat your
soda ash to a higher temperature, is important to cool to
this temperature range to prevent this hydrolysis, but there is no
need to cool all the way down to room temperature. Just cool down to
where it is comfortable to handle (below 40 degrees C., or 104 F.).
Temperatures below 70 to 80 degrees Fahrenheit should be avoided, as they can slow reaction time of "cold water" dyes dramatically.