Soapmakers: Thoughts on calculating water or using discounts
Recently I have become aware of some difficulties soap makers are having while trying to figure their water needs. Let me try to help clear the air (water?) here.
1) Water is needed in your soap making process. This is not an ingredient that needs to be weighed to 1/100th of an ounce accuracy. Any excess water will evaporate so only worry about non-variable ingredients when you spend time weighing.
2) Always base your water needs on the amount of fat and never the amount of lye. Recent comments to me indicate that some people are teaching to use an amount of water that is double the amount of the lye needed. Let’s cover two examples:
a batch of soap that is 16 ounces of oils, the lye calculation needs 3.68 ounces, water would then be 7.36 ounces
second batch of soap that is 16 ounces of oils, the lye calculation needs 1.55 ounces, water would then be 3.10 ounces.
For the first batch in this example 7.36 ounces of water is quite fluid yet still workable. It will take longer for the soap to cure because the extra water must evaporate. Trace may be slow to come because of the excess water.
The second batch has too little water, trace will happen very quickly, it will be difficult to color or scent because the soap progresses too fast. Both batches are the same size, 16 ounces of fat. The first batch will likely be 22 to 23 ounces of finished soap, the second batch will likely be 20 to 21 ounces of finished soap.
How to correctly calculate the amount of water needed for each batch:
Calculate the amount of fat you are using. Multiply this amount by 32 to 42%. If you live where: the air is so dry your sheets crunch when you crawl into bed, daily reports of how low the relative humidity is in your region appear on the evening news, without supplemented water your lawn will be brown for 11 months of the year then you know you need closer to the 42%. This is about to 6.75 fluid ounces per lb of fats. If you can’t remember when the last dry day happened, mold is a constant problem, moss grows on every roof top in your city, and everyone uses the term muggy or damp on a daily basis, or if you own and use a rain coat/slicker regularly – you should use closer to 32% which is about to 5 fl oz per lb of fats. You may have needs to use more or less water than these amounts but at least you are now calculating for your needs instead of aiming for moving, unreliable target.
Think I might have missed the mark? If so, then why do we use different amounts of scenting oils when we make peppermint soap vs vanilla soap? Different needs require different amounts. Use what you need, not what is excessive or too little.
Need help with your recipes? Just comment on this blog and I will help walk you through the math.