"Soap Boiler"

[donniej]

A long, long time ago soap makers were called "soap boilers". I've read a lot of old soapmaking manuals and here's why...

First you render your used cooking grease or fatty tissue from the butcher shop. Then heat it until liquid and mix in a mixture of lye and water; so far, pretty familiar stuff so far.... but here's where it changes. Next brine was mixed in, brine is a mixture of 1/3 salt and 2/3 water. The soap can not stay dissolved in the salt water so it floats to the top of the kettle in the form of curds.

The curds are removed and washed to remove excess lye. After washing, the curds are "slabbed" into molds. You know the rest.

The water from the first kettle is still full of water, salt, lye and glycerin. With enough salt, the glycerin will fall out and sink to the bottom. Using a cone bottom tank with a valve at the bottom, the glycerin is drained. If you add enough lye, the salt will fall out as well, the salt is then drained off for reuse. The lye/water stays in the tank and is also reused.

The main reasons the glycerin was removed is to sell. I've read that the profit margin on soap was so thin that the sale of the glycerin was the only way to be profitable.

 

[carebear]

other fun things to know:

this process worked well because back in the olden days they could use excessive lye (which was important because they never really knew how strong their lye was, or precisely how much they needed). further, the "lye" that was created by dripping water through ashes was primarily potassium based - not sodium as our sodium hydroxide was. which meant the soap was soooooooft. by boiling with salt (SODIUM chloride), some of the potassium was swapped out for sodium which meant the resulting soap was harder.

nifty, hunh?

 

[donniej]

I've actually done a ton of research on the manufacturer of caustics as well, not entirely for soapmaking reasons.

Historically, most areas did get there caustic from wood ash. Specifically, the ash from hard woods. This gives an imprure potassium carbonate. Home soapmakers could have roughly measured its purity by floating a potato in it, the more the potato sank, the stronger the solution. This impure poassium carbonate was called potash. Industrial users would cook potash in a furnace to burn off impurities, the purified potash was called pearlash.

Potash/pearlash is also a critical ingredient for the manufacturing of cotton. It was so important that it was a main reason for the colonization of the USA, as England was virtually out of trees.

Sodium carbonate was made the same way but used seewead which contains sodium instead of potassium.

These were used most of the time where caustics were needed, up into the mid/late 1700's at least. At some point (I don't know when) it was discovered that boiling carbonates with burnt lime (calcium oxide) yields hydroxides.

There was however a huge "X Prize" type prize being offered by King Louis of France for the disocvery of a method of making caustics that doesn't require mass burning of trees. LeBlanc developed his process and "Soda Works" quickly began popping up. More efficient process's followed.

In soap making manuals that I've read from the mid 1800's, it says that only rural areas of Germany were still making soaps from wood ash derived potash.

 

[Vintageliving]

A long, long time ago ...brine is a mixture of 1/3 salt and 2/3 salt....

Donnie, did you mean for one of those to be water?

This is very interesting.

Could post more about the Soap Works?

Thanks!

 

[donniej]

Fixed
Yes, 1/3 salt, 2/3 water.

What soap works are you asking about?

 

[Vintageliving]

...
method of making caustics that doesn't require mass burning of trees. LeBlanc developed his process and "Soda Works" quickly began popping up. More efficient process's followed.

In soap making manuals that I've read from the mid 1800's, it says that only rural areas of Germany were still making soaps from wood ash derived potash.

Donnie, thanks.

Ooops, I meant Soda Works. Sorry.

When I lived in Germany, I visited a living history museum. One of the chores they revived was making lye from wood ash. Was a fascinating museum.

Thanks very much for doing all the reading and posting!

 

[donniej]

I don't know too much about the soda works. In the late 1700's the LeBlanc process revolutionized the caustics industry but many others soon followed. There were 3 or 4 different process's that followed, all with a large degree of popularity... kind of like Friendster -> Myspace -> Facebook
BTW, LeBlanc never got his prize money (due to the French revolution) and died broke.

These days sodium hydroxide is made from salt water. Using electrolysis the sodium chloride (salt) and hydrogen oxide (water) are split into chlorine, sodium hydroxide and water. Or....
NaCl + H20 -> Cl + NaOH + H2O.

This is done with using simple electrolysis like you may have done in highschool chemistry except a membrane is used to keep the electrodes separated. I believe this keeps the chlorine separate from the lye but I'm not positive about that.

 

[Vintageliving]

Donnie, thanks for your post. I'm going to read more on this.