Daily Archives: July 13, 2020

Can I use soda ash in my front loader washer to soften my hard water?

Name: Mary
Country or region: United States

Message: Hello: I am wondering if I can use soda ash in my front loader washer to soften my hard water. I am a beginner dyer and had to purchase some soda ash and wondered if I can use the same product for dyeing and as a water softener.

I have also seen washing soda (by Arm & Hammer) used as a water softener. Is that better? If possible, I’d like to use one product for dyeing and water softening. Please advise. Your comments/suggestions would be most appreciated. Mary

Soda ash is not a good water softener for dyeing.

What works really well as a water softener for dyeing is sodium hexametaphosphate (also known as Metaphos, and formerly sold under the name of Calgon). Here in the US, I recommend that you order Water Softener from Dharma Trading Company, or Water Softener from Colorado Wholesale Dye (they have really good prices!), or Metaphos from PRO Chemical & Dye, or buy Jacquard Products brand Calgon from an art supply store that sells dyes from Jacquard Products. (See Sources for Dyeing Supplies Around the World for contact information for these and other suppliers.) Do NOT buy Calgon that is not specifically labeled as being Jacquard brand or sodium hexametahosphate; although “calgon” used to mean sodium hexametaphosphate, the Calgon company now sells entirely different products, such as sodium citrate or polycarboxylate, under the same name, which can cause real problems in dyeing. As long as you buy a product with “hexametaphosphate” in the fine print, you’ll be fine.

Water softening is the removal of hard water metal ions, specifically calcium and magnesium. Calcium forms complexes with some unattached dye molecules that are difficult to wash out, which results in some slowly-released unattached dye that bleeds in the laundry; it can also produce unwanted spotting as the dyes attach to the fabric. Sodium hexametaphosphate binds to the calcium and magnesium, making them water soluble, and removing the problems caused for dyeing by hard water.

We frequently use sodium carbonate to increase the pH so that cellulose can react with fiber reactive dyes. Although sodium carbonate is listed as a water softener for some purposes, using sodium carbonate does not solve the calcium problem when dyeing. It’s just as useless for this purpose in a front-loading machine as in a top-loader. Sodium carbonate reacts with the calcium in hard water to form insoluble calcium carbonate, which is deposited not only on the sides of a sink or bathtub, but also on the fabric, interfering with the ability of dye to evenly reach the fiber that you are dyeing. The water in the dyebath is, technically, softened by this reaction, because you end up with less calcium in the water; however, putting insoluble calcium carbonate onto your fabric does you no good at all.

A household water softening device uses a resin to replace the calcium ions with sodium ions, but this is not possible without the water softening equipment. You can’t do this in a washing machine.

Washing soda, including that sold by Arm & Hammer, is nothing more than sodium carbonate with a few extra water molecules complexed to it. It is not better or worse as a water softener than soda ash is; they act exactly the same, which is to say, neither is useful as a water softener for dyeing, and both work very well as a fixative for fiber reactive dyes such as Procion dye. You can always use washing soda (sodium carbonate decahydrate) as a substitute for soda ash (anhydrous sodium carbonate), or vice versa, if you remember that washing soda has more volume and more weight per a given amount of sodium carbonate than soda ash does. You need to use 2.7 times as much washing soda as a substitute for soda ash, if measuring by weight, or 4.6 times as much if measuring by volume, to get the exact same number of sodium carbonate molecules. However, most of our dyeing recipes include a comfortable excess of sodium carbonate, so it’s usually not all that important if you forget to increase the amount you use.

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