Making Soap before the Invention of Thermometers

How was the temperature controlled in making soap prior to thermometers being so easily available? 95 degrees seems to be a very set temperature.
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I think these days when making soap, and even cheese for that matter, we get hung up on using modern inventions like thermometers in such a way that we don't realize that if the temperature fluctuated 5-10 degrees either way, it probably wouldn't make any difference to the end result.

Certainly people were making soap well before Roman times, and throughout the Middle Ages, and they didn't have anything like a thermometer to measure heat for this process. Remember too, that they were also using lye made directly from wood ash and so the process was very much longer. In fact, it could take anything from 6-8 hours for the soap to finally saponify depending on the strength of the lye.

So how would the soap maker know that they had reached the right temperature without a thermometer in making soap? Well, they would certainly be able to tell just be looking at it, but more importantly they would often take a bit of the mixture out of the pot and place a small amount on the tongue. If it had a "bite" to it, they continued to boil the mixture longer and taste it again until there was no further "bite" experienced on the tongue.

Personally, we are very thankful for the invention of the thermometer!

Regards
Countryfarm Lifestyles