Name: miles
Message: I need to dye the bottom half of a bunch of shirts.  They are natural color organic cotton shirts and I need the bottom 5-7 inches dyed an aqua green color, like they were dipped. The problem I'm having is that I need a clean sharp line where the dye color ends.  Is there a method of dying that you would suggest to do this? If I just dipped them in MX dye I would imagine that the dye would creep up the cotton fiber making a very uneven, fuzzy line.  Is this true?

Yes, you're right. You do tend to see  a fairly fuzzy edge at the top of the line of dye, when you dip one section of fabric into the dye. What may be more problematic is the fact that green dyes are almost invariably mixtures of blue and yellow dyes, so the blue dyes may migrate farther than the yellow, or vice versa, resulting in a halo of a different hue. I doubt that you want a blue or yellow edge on your aqua green.

There are several different possible solutions. The simplest might be to thicken your dye with sodium alginate. This reduces the tendency of the dye solution to spread on the fabric. You can mix up your Procion Mx dye as usual, then add sodium alginate which you have already dissolved in water. It takes a bit of time to get alginate to dissolve thoroughly. You should dissolve the alginate the day before you apply the dye, or else start by suspending the alginate in alcohol or vegetable oil and then mixing it. This procedure is described on my page about "Sodium alginate, Superclear, and other dye thickeners". The exact amount of alginate you need to use is difficult to predict, since different batches of alginate vary in strength. Alginate can be used with MX dye at a wide range of different thicknesses. Do a test, possibly several tests, before you dye a large number of shirts.

Another option would be to apply a a horizontal line of resist to your shirts before dyeing them. The resist will serve as a dam, to prevent the dye from creeping beyond it on your shirts. It will also prevent color separation at the edge. Melted beeswax could be used as in batik, or you could use a water-soluble resist such as Elmer's Blue School Gel. (See "Immersion Dyeing with Water Soluble Resist".) The beeswax is more straightforward to use, because it will not dissolve in a dyebath even after some soaking, but the water-soluble resists are less trouble to wash out. Beeswax must be removed by ironing or boiling, which is a lot of trouble. (Many people recommend dry-cleaning for wax removal, but the dry cleaners I've used do not remove any of the wax at all.) A relatively new alternative is soy wax, which is melted in the same way as beeswax for batik, but does not require the melting temperature to be as high, and it can be washed out in hot water. The best soy wax to use is the type used to make hard pillar candles. Do not use the more liquid or gel type of soy wax, which is used only for candles that remain in their containers for use. You can order the correct hardness of soy wax from a dye supplier such as PRO Chemical & Dye, if you want to be sure of getting the right stuff.

I think that my choice, in your situation, would be to order some soy wax and use it to make a fairly thick line where you want the edge of the dye to be. It may be necessary to apply it to both sides of the fabric, inside and outside the shirts. Be careful not to overwhelm the wax by getting more dye on the shirt than the wax can hold back. The soy wax should not be expected to be as sturdy as batik wax. Even batik wax can degrade a bit in the soda ash used with Procion MX dyes.