Stock solutions
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.



















