To do this, first figure the total amount of soap that you would make in your chosen mold, if it was filled with a fresh batch of soap. For the mold I used in this project, that was 51 ounces -- that is, using my standard recipe, the total weight of the lye, water, and oils is 51 ounces.
Next, figure out the percentage of shreds you want in the batch. I recommend between 25% to 35%. I chose to make this batch with 1/3, or 33%. If you want just a sprinkling of shreds, use as little as 15% or 20%. If you want a really shred-filled bar, you can go up to as high as about 50%.
Based on the total amount of soap you mold will hold, figure out the weight of that percentage of shreds. For example, with my 51 ounce batch of soap, and my 33% of shreds, that came out to be 17 ounces of shreds.
Subtract those shreds from your total amount of soap recipe, and then scale your recipe down to make that amount of soap. For example, in this case, after deducting 17 ounces of shreds, I was left with 34 ounces of soap. So I scaled my basic soap recipe down to 34 ounces. Some lye calculators will do this for you easily, as will software programs like Soapmaker. However you do it, just be sure that you're scaling down your recipe to account for the shreds - the already made soap.
Then...make your shreds.
Big shreds, little shreds, long shreds, short shreds, curly shreds, straight shreds - you're only limited by your imagination and your cheese grater!
