Stock solutions

30 September 2007

 What concentration to make your stock soultions?

Again to follow up on what Peg said  that I used 0.01% stocks.  Well sometimes I do and sometimes I don’t.  When I worked with stock solutions all the time , I usually made Lanaset Stocks at 1%.  The Lanaset, and most acid dyes, have limited solubility and 1% is achievable with most of the dyes without additives. Fiber reactive I usually make 2%, they are more soluble and require higher DOS.

When I started dyeing batches of 2500-3000g of silk the volume of stock was too large.
For example dyeing 3000g of silk, a medium DOS of 3% with stocks that are 1% requires

3000g x DOS of 3%/1% stock =9000g or mL of stock

9000mL= 9L 

That is a lot of stock!  Now I used to make the stock in 1/2 gallon canning jars, that would only hold 1800ml so this would be a big, big chore to make 9000ml of stock. It is easier just to weigh out the dyes  powders for each batch.  90g of dye, even if it is divided up into 5 colors is still doable  even with a balance that only weighs to 1g.

But dyeing 450g of silk to the same DOS would require 1350ml of 1% stock which is convenient.

But when I sample for new colors I dye 5g swatches of silk.  So the same formula

5g x DOS 3%/1% stock=15 g=15ml 

gives me 15ml of dye stock.  So what would the effect of a drop of dye stock solution falling off the out side of the pipet into the dye bath.  Now a drop of aqueous solution we can guess to be about 0.2 ml, and

0.2ml/15ml= 1%.

So an inadvert drop can cause a 1% error.  If I go to a pale color and the total dye stock required for the 5g swatch is reduced to 2ml, the drop size stays the same but now it is a 10% error.  Makes it difficult to reproduce the color on a larger batch and that is the reason for dyeing the swatch.

There is a very simple way to increase the accuracy; dilute the stock so that you are measuring out a larger amount of stock and the drop, still at 0.2ml,  will be insignificant.  1% stock/ 10 will give me 0.1%.  So I take 10 ml of the 1% stock and add water to 100 ml mark; voila  100 ml of 0.1% stock. Repeating; in a 100 ml graduate cylinder I fill it to 10 ml with the old stock and then to 100ml mark with water. Easy! So dyeing a 5g swatch a pale color, DOS=0.3% with the 0.1% stock;

5g x DOS 0.3%/stock 0.1% =15 ml

and a drop is back to 1% error.  If I want even more accuracy, say because I’m dyeing neutrals,  I can dilute 10ml of this solution to 100ml again and have a 0.01% stock and measure out 150 ml.

The conclusion here the amount of  silk or fiber you are dyeing at one time , WOF or WOG, determines if you will work with stocks, and the concentration of the stocks. 

The numbers I have used in the above examples are total dye and that total might be divided into 3-5 colors. Dividing 2 ml among 3 colors would require me to measure volumes of less than 1 ml.  There was a time when I did not have equipment to measure small volumes. I could weigh the solution if I had an accurate balance; 0.35 ml=0.35g.  Or I could make  the more dilute stock and measure the larger volumes with the equipment that I did have.

This is all grade school grade math and the point is to enable you to do what you want to do with the equipment that you have. 



2 Responses to “Stock solutions”

  1. I should have been more specific in my statement! You had said you use .01% solutions when you were dyeing multiple small samples. It’s easier and more accurate to measure out say 50 ml than say 1/4 of a ml.
    Your challenge sounds fascinating. I love your piece.


  2. Thank you for the grade school math! I am retaining your statement: “I can dilute 10ml of this solution to 100ml again and have a 0.01% stock and measure out 150 ml.” As long as I have that in my head I can create any amount of of 0.01 solution that I want. When I see this, metrics are so very simple. Again, thank you.!


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