One of the questions I am asked most often is “How much fiber do I need to buy to make (whatever)”. The answer is always the same. It depends. It depends on the finished size of the project, the design of the project, and on whether the spinner is starting with a grease fleece or already prepared fibers. Here’s how to figure it out.

Let’s assume that we’re going to start with a grease fleece. What we know at this point is the weight of the fleece and the fact that we are going to lose some of that weight when we wash it. What we need to figure out is how much clean fleece we will have after scouring. The only way to get this information is to wash a sample. Because this sample will be used for a lot of things, let’s start with a good sized sample of grease fleece – say 1 lb.

Weigh out 1 lb of grease wool and scour and dry it. Then weigh the clean, dry wool.
Here is the formula for figuring the percentage of weight loss:

(Grease wt.) minus (Washed wt.) X 100 = percentage of weight lost
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Grease weight

So, if the grease weight is 1 lb and the clean weight is 12 ounces. We have 16 – 12 = 4. 4 divided by 16 = .25 X 100 = 25. There is a 25 percent loss of weight in scouring. So if the grease fleece weighs 10 lbs., then 2 ½ lbs will be lost in washing and there will be 7 ½ pounds (75%) of scoured fleece remaining to be processed.

The next step is figuring out how much of the scoured fleece will be lost in processing.
When processing the sample, include every step that you plan to use to prepare the fibers for spinning for your project. Weigh the unprocessed fibers, then process them exactly as planned for your project and then weigh the processed fibers. Here is the formula for figuring processing loss:

(Washed wt.) minus (processed wt.) X 100 = % of weight lost
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Scoured Weight

We had 12 ounces left after scouring the 1 lb sample, and let’s say that the processed fibers weigh 10 ounces so 12 – 10 = 2. 2 divided by 12 = .166 X 100 = 16.6 % processing loss. We will have 7 ½ lbs of scoured fleece and will lose 16.6 percent of it in processing so there will be a yield of 83.4% or 6.25 pounds of processed fibers remaining from the 10 lb. fleece.