How much soda ash should I use to scour fabric before dyeing?

Name: Leslie

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Country or region: East coast USA

Message: Hi, Paula--

I've tried searching for the answer to this, believe me...

I want to scour a small amount of PFD cotton (3 yards), and wondered if I can do it in our big utility tub with very hot water, Synthrapol and soda ash. If so, what would be the amount of soda ash to add to the water? Is there a rule of thumb for soda ash per gallon of water for smaller quantities of fabric, like, say, per yard? Or is the amount of soda ash the same as in the cold-water immersion process per gallon? I really don't want to put such a small amount of fabric in my washer, which doesn't do such small loads....

The purpose of the scouring step is to clean your fabric before dyeing. It helps in removing invisible sizing or other finishes that can interfere with dyeing, though there are some finishes that can't be removed so easily. Don't confuse the soda ash used in scouring with the soda ash used in fixing the dye. The soda ash used in the scouring stage will be rinsed out, so it won't do anything to help fix your dye.

The very best way to pre-scour fabric, before dyeing, is to boil the fabric on the stovetop. This is more effective than pre-scouring at the cooler temperatures that are all you can manage in a washing machine. You should not use an aluminum pot for this step, because aluminum reacts badly with soda ash. A stainless steel or enameled pot is ideal.

If you don't want to use a cooking pot for your scouring, just use your utility tub, a sink, or a large bucket, with the hottest water you can get. In very cold weather, you may want to warm the tub first with hot water, drain it, and then scour your fabric with more hot water. You will need to stir or agitate the fabric repeatedly in the water, along with the soda ash and Synthrapol. If you're going to get your hands in the water, be sure to wear rubber gloves, such as the ones used for dishwashing, that are a long enough to protect your wrists, because you don't want to get soda ash on your hands unnecessarily, and, ideally, the water should be scalding hot anyway.

PRO Chemical & Dye says to use half a teaspoon (2 gm) of soda ash and half a teaspoon (2.5 ml) of Synthrapol for scouring each pound of fabric; they don't specify how much water to use, but it should be a large enough amount that the fabric can move freely in it. It's really not critical exactly how much soda ash you use. It's best to weigh your fabric, while it's still dry, to know how much you have, but they give a rough estimate that one pound of fabric equals 3 to 4 yards of cotton muslin. Of course, heavier fabrics weigh more per yard.

After scouring your fabric, drain off the water, which may be visibly dirty depending on the cotton, and rinse with clean water. You can use the spin cycle of some washing machines to remove excess water at this step, without having to fill the washing machine or run a full cycle.

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Posted: Saturday - November 12, 2011 at 01:25 PM

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How much soda ash should I use to scour fabric before dyeing?

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