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.
Comments
Posted by: Peg in South Carolina | October 2, 2007 11:56 AM
Posted by: Peg in South Carolina | October 2, 2007 12:03 PM