My name is Claire and I have to do a science fair project for school. The subject I have chosen to base my project on is Fabric Dyeing. The problem I have chosen is "Which fibers, natural (cotten, linen, silk) or synethic (polyester, rayon, nylon) do natural dyes take to better?" and I was wondering if you could send me some information on this subject. If you could, it would be very helpful. Thank you for your time.

Do not group rayon and nylon with polyester! Nylon is easily dyed with the same acid dyes that work on wool, because it contains an amide group much like that found in proteins. Even though it is synthetic, it acts like a natural fiber, because it is chemically similar to wool. Rayon is a fiber made of cellulose, just like cotton, and dyes the same as cotton, though the colors are brighter on rayon because the processing makes the cellulose molecules more easily reached by the dye. The cellulose in rayon is extracted from wood.

See "Dyeing Polyester with Disperse Dyes".

I think it would be great to compare polyester to cotton, and/or to silk, and/or to linen. Cotton and linen are almost identical, both being made of cellulose. Silk is a special case and can be dyed with fiber reactive dyes (see "Fiber Reactive Dyes") the same as cotton and rayon and linen, AND it can also be dyed with acid dyes (see "Dyes for Protein Fibers"). Wool is badly damaged by the high pH used with most fiber reactive dyes, though it will accept the dye.

If you use fiber reactive dye and soda ash (see "Hand Dyeing - How to Do It: basic recipe for Procion MX dyes on cellulose or silk", nylon will react much the same as polyester. Nylon does not accept dye at the high pHs required to dye cotton.

It would probably be best to avoid the use of all-purpose dye (brands of which include Rit Tint And Dye, Dylon Multi-Purpose Dye, and Tintex Hot Dye). It is a mixture of two completely different kinds of dye, which could confuse matters for your experiments. One, called acid dye, will work on wool, silk, and nylon, and the other, called direct dye, will work on cotton, but not nearly as well as fiber reactive dye. (It continues to bleed dye every time you wash it, forever! Fiber reactive dye doesn't do that.) If you use all-purpose dye, you should discuss this in your project write-up. It might be simpler to express-order some fiber reactive dye, such as Procion MX dye, from ProChem (see "Sources for supplies"), or call around your local fabric stores to see if anyone sells Dylon Cold Water dye, which is also made up of fiber reactive dye. Make sure it says Cold water! Dylon also sells all-purpose dye under the name of Dylon Multi-Purpose dye. If you do use all-purpose dye, follow the instructions for "How to Tie Dye with all-purpose Dye" or ProChem's "Immersion Dyeing using Diazol Direct Dyes".