Name: LauraLynn

Country: USA
Message: What is the best and most cost effective way to overdye 40 to 50 printed white t shirts to red? How much dye would I need?

The most cost-effective method depends on whether you want the dye to last well on the shirts even after they are washed.

The cheapest dyes for 100% cotton shirts are the direct dyes. These are the same type of dye that is found in the mixture known as all-purpose dye, but it's much less expensive when bought in bulk. Don't buy all-purpose dye, as it is extremely expensive per garment. If you mail-order direct dye from a good dye supplier, such as Dharma Trading Company under their name "Industrial Dyes", you can get enough dye to color a hundred pounds of clothing for under seven dollars, plus about ten dollars shipping. The same amount of dye in the form of the little boxes of Rit All Purpose Dye would cost four or five hundred dollars! The quality of the dye is similar, too.

The cheapest and best long-lasting dye for cotton t-shirts is Procion MX. Because it's a fiber reactive dye, it forms a permanent bond to the fiber which will last for years. For fifty shirts, or about twenty-five pounds of cotton fabric, you'll need about a pound of this sort of dye, which will cost about $21 plus shipping from a good dye supplier such as PRO Chemical & Dye or Dharma Trading Company. You'll also need a large quantity of common table salt, and some soda ash or washing soda to enable the dye to react with the fiber. Use more dye for a more intense color, or less dye for a pastel color.

You can make the direct dye in the Industrial Dyes last much better through laundering if you after-treat them with a cationic dye fixative, such as Retayne. Of course, this adds to the price, but not a lot, since this product is inexpensive when purchased from a dye supplier. I prefer the fiber reactive dyes, but direct dye plus fixative is cheaper.

To dye so many shirts a solid color, you will want to do your dyeing in the washing machine; this will not hurt the machine. Note that a standard washing machine load is about five to eight pounds of fabric. Don't overload your machine; the shirts must be able to move freely in the water if you are to get a smooth solid color. You'll need to split up your pile of shirts into several loads, unless you have access to  a commercial dyeing machine. Use a top-loading washing machine, not a front-loader. Find a good recipe and follow it closely. See "How can I dye clothing or fabric in the washing machine?".

Be careful when buying your shirts to make sure that they are 100% cotton, not a poly/cotton blend, and that they have not been treated to make them stain resistant, as that treatment will also resist dye. Shirts that have been screen-printed with a design in a strongly contrasting color look very good when dyed, if the color of the printing is very dark or else opaque; it does not matter whether you dye before or after the shirts are screen-printed.

See also the table "comparison of dye costs" in the Dye Forum, which compares the cost of enough dye to color one pound of fiber, including different dyes for different fibers.

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