Name: nille

Message: Hello
I have some yarn which are a mixture of wool and viscose. What type of dye do you recommend? And should I use vingar or salt or something else to get a permanent result on both the wool and the viscose?
Thanks for all the very usefull information you give.
Kind regards
Nille

I see from your address that you are in Denmark. A good source for dyes in Denmark is Granat Farvekompagniet.

One possibility is to combine the use of direct dyes for the cellulose fiber (viscose rayon, like cotton, is made of cellulose) with acid dyes for the wool. It is possible to use both direct dyes and acid dyes at the same time, in the same dyebath; this is what you do if you use an all-purpose dye mixture, such as Rit All Purpose Tint and Dye, Tintex Easy Fabric Dye, or Dylon Multi Purpose dye. Note that Dylon Machine dye and Dylon Hand dye contain fiber reactive dyes, along with a high-pH chemical that is not suitable for dyeing wool; if you buy Dylon dye, make certain that the label recommends its use for wool.

All-purpose dyes have some drawbacks. All purpose dyes contain both direct dyes for cellulose and acid dyes for wool. Direct dye, as a rule, is poorly washfast; it tends to bleed in the laundry and fade relatively quickly. The type of acid dye used in all-purpose dye mixtures is Leveling Acid dye, which is the least washfast of wool dyes. If you use all-purpose dye to dye anything, you must be prepared to launder whatever you dye gently, in cool water, by hand, separately from other colors, for the life of the item.

You can correct for the poor washfastness of all-purpose dyes by soaking your dyed yarn in hot water with a cationic dye fixative, such as Retayne, after you have finished dyeing and rinsing out. It's worth asking your dye supplier if they carry this or a similar product. All the major dye suppliers in the US and Australia do, and the textile industry all over the world uses similar cationic dye fixatives for direct dyes.

With any acid dye, including the acid dye in all-purpose dye mixtures, it is important to add some acid to the dyebath. If you are using an all-purpose dye mixture, add 100 ml of distilled white vinegar (which contains 5% acetic acid) for every four liters of water (that's about 7 tablespoons per gallon). The acid is useless for dyeing viscose or cotton, but not harmful, and it is important for dyeing wool. Add salt only if it is called for by the recipe supplied with the dye that you purchase. 

An alternative for dyeing a wool/cellulose fiber blend is to use a fiber reactive dye, such as Procion MX dye or Remazol dye, at a pH which is not as high as generally desired for dyeing cellulose fibers, but not an acidic pH. Do not add vinegar or any other acid if you take this approach. Instead, mix sodium bicarbonate (also known as baking soda or NaHCo3, not soda ash, which is Na2CO3) with water, approximately 250 ml per 4 liters of water in the dyebath, and, using pH paper, check the pH. You want a pH of around 8 or 9 for this purpose, high enough to permit some reaction of the viscose with the fiber reactive dye, but low enough not to damage the wool, as the usual pH for fiber reactive dyes on cellulose would do. USe more or less sodium bicarbonate as needed in order to reach a pH between 8 and 9. You do not need to heat the dyebath to boiling as you would do with acid dyes and direct dyes, or with the all-purpose dyes that contain them; instead, aim for the ideal temperature for the fiber reactive dye you choose. For Procion MX dye, this would be 35°C to 45°C (95°F to 105°F); for Remazol dyes, this would be 40°C to 60°C (104°F to 140°F). Since the dye reaction will not proceed as quickly at a pH of 8 to 9 as it will at the optimal pH of 10.5 to 11.5, you will need to make sure that the temperature is optimal, that you use enough dye powder, and that you allow more time than you normally would, preferably overnight. (For ideas on how to warm your dye reaction, see  the page "What is the effect of temperature on fiber reactive dyes?", scrolling down to the section on "Ways to increase your reaction temperature".

For more information on the question of how to simultaneously dye blends of animal fibers with plant fibers, see "Two ways to dye wool/cotton blends", in the Dye Forum from October 2008.

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