Name: Renee

Country or region: Northwest USA

Message: Hi Paula,
My 11yo daughter is doing a science project on the effects of Rit dye on white 100% cotton, 100% polyester fleece and felt, 100% cotton denim, 100% nylon netting and, finally, 96% cotton/4%spandex fabrics. Do you have any rcommendations for her? Will a mixture of the dye and salt or dye and vinegar have and special effects? Do you know why the effects will scientifically be different or a website we could visit for these type of questions? The experiment is due April 30th. Thank you for anything you can help with!


Rit dye is a mixture called all-purpose dye, which contains both a cotton dye called direct dye, and a dye for wool and nylon that is called acid dye. It is a hot water dye, as both direct dyes and acid dyes require a considerable amount of heat in order to perform at their best. Please start by reading the following pages:
"All Purpose Dyes"
"About Direct Dyes", and
"Acid Dyes".

All-purpose dyes are not the highest quality type of dyes, because they tend to fade rather quickly, and they bleed badly in the laundry. However, since they contain more than one type of dye, they will color a wide range of fibers. They will work on cotton, including cotton denim and the cotton portion of cotton/spandex blends; they will also work on nylon, as long as it doesn't have any sort of coating that will repel the dye. They will not work on polyester, whether it is in the form of fleece or felt. It makes a nice project to compare the effects of a dye on both natural and synthetic fibers, since you can generally see a big difference. Nylon is a synthetic fiber, but it is an interesting exception for dyeing, because it chemically resembles the proteins found in wool, so it dyes like wool, instead of like polyester.

To learn more about what dyes work on different fibers, please read the following pages:
"FAQ: How to dye nylon or polyamide", 
"How to Dye Cotton", and
"Dyeing Polyester with Disperse Dyes". (There is no disperse dye in Rit all-purpose dye, so polyester cannot be dyed permanently using all-purpose dye.)

The type of dye that works on nylon is called acid dye. It is included in the Rit all-purpose dye mixture. However, there is no acid included in the dye mixture. Dyeing nylon will work much better if you add some acid, along with the dye, to lower the pH. The most convenient acid to use in your kitchen is ordinary vinegar. A good quantity to use is 25 milliliters of ordinary white vinegar per liter of dyebath; this works out to one tablespoon plus two teaspoons of vinegar, in one quart of water, or one teaspoon of vinegar in three-quarters of a cup of water.

Salt is included in the Rit dye mixture. You have enough variables already, and it will be difficult to tell what effect the salt has. I recommend that you add more salt only if the dye package directs you to do so, and to use the same concentration of salt in each case.

A good way to dye several different types of fiber at once, without one fiber interfering with another fiber, is to use quart-sized canning jars. You can place a piece of fabric or yarn in each jar, add the dye after dissolving it in water, and add any other chemicals, as well. Then you can place the jars inside a large cooking pot with some water and boil them for half an hour or an hour. It's not a good idea to dye two different types of fiber in a single dyebath, because one fiber may take up the dye so quickly that their is none left for another fiber, which would give misleading results.

You should not use your good cooking pots to dye fabric. Textile dyes, such as Rit dye, are not approved for use on food preparation surfaces. There are a couple of other safety precautions you should follow. You should always wear a dust mask when working with dye powder, after you have opened the package of dye and before you have gotten it all dissolved in water; you can buy a dust mask at the hardware store. This is a good practice when working with any powder that might be irritating or allergenic. You should also always wear plastic, latex, or rubber gloves when working with household chemicals, including dye. You can buy these at the hardware store or the drug store.

If you do not heat the fabric with the dyes on the stovetop, they will not attach as firmly, but they will probably still attach well enough for the project to work. At least use the hottest tap water available, because heat is important in helping both direct dyes and acid dyes attach to their fibers. It would be interesting to do a project comparing cold water, hot water, and boiling, but this is too complicated to include in your current project; just make sure that all of the fabrics get the same temperature of water, so that they are comparable. I would like to recommend that you use the stovetop method, instead of just using hot tap water.

Washing out the excess dye from the fabric, after dyeing, is an important step. You may find that the polyester temporarily appears to have taken up the all-purpose dye. The color of the fabric before washing is meaningless, however. You can rinse the fabric by hand in the sink (wearing rubber gloves to protect against unattached dye, which will stain your hands, and to help protect against hot water), or you can put a number of swatches of fabric into a mesh lingerie bag and wash them in the washing machine.

There have been many other questions sent to me, asking about using dyes in science fair projects. You may find it useful to browse through my answers to them. They are a sub-category in my "All About Hand Dyeing Q&A" blog. Here is a direct link to the "Schoolwork" category of the blog. Some of the questions are similar in level to your daughter's project; just skip over any which are at too advanced a level. Your daughter can use any of these pages as references in the bibliography section at the end of her project. You will see that your letter is, today, the most recent entry in the blog.

Good luck to your daughter in working on her project.

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