Name: Tom

Message: I have EXTREMELY hard water, so I will be bringing some in. I have access to R.O. water & R.O./DI water... which is better for mixing Dyes? (RO= Revese Osmosis, & RO/DI is Revers Osmosis/Deionized)

Do you know what contaminants are in your water supply to worry about? The hardness minerals in water are calcium and magnesium. Metals such as iron and copper will also interfere with dyeing; iron in particular will "sadden" the colors of many dyes, making them duller, darker, and less brilliant.

You do not have to bring in water that is treated by reverse osmosis or deionization if you can treat your water with the water softener chemical, sodium hexametaphosphate. (See "Dyeing with hard water: water softeners, distilled water, and spring water".) Your dye supplier should carry this substance. Dharma Trading Company calls it "Water Softener", PRO Chemical & Dye calls it "Metaphos", and Jacquard Products and Fibrecrafts call it "Calgon". This chemical is sold in powder form: do not substitute liquid Calgon brand products! They contain an entirely different type of chemical, the polycarboxylates, which may interfere with dyeing. The amount of sodium hexametaphosphate that you should use depends on how much hardness is in your water. See "how much metaphos to use" in the Dye Forum.

Whether a system that is labeled "reverse osmosis" is superior or inferior to one labeled "reverse osmosis/deionizing" depends on how much of the hardness minerals or other problem minerals are present. Check the information provided by the manufacturers. You want a system that will remove the vast majority of any calcium and/or magnesium ions. A home deionizer will remove polyvalent ions such as calcium and magnesium (both of which have a charge per ion of +2) by substituting sodium ions. If you have a serious problem with iron, contact the manufacturer and ask how much of the iron in the water their systems will remove.

Distilled water is the best, as far as freedom from unwanted minerals is concerned, but it is almost never necessary to use distilled water.

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