Salt, Soda ash and potash

Submitted by Mike Collins on 11/08/2002. ( )


I've searched the archives before posting but I'd like to ask for help a step at a time so as to be sure of my ground. By way of an introduction the name's Mike, resident in UK currently studying for my MA at University College London. As a very young man I worked at Rowland Ward Ltd, a firm I'm sure you'll know of as taxidermists :-)
I didn't stay more than a year at Rowlnad Ward, moving to Ireland where I first started in archaeology.

Now, in Irish prehistory I'm wondering where and how people were obtaining their salt from. It's often claimed in my literature that salt was an essential in a range of craft activities and I'm hoping to verify this before moving on to further researching indigenous production of salt either by using seaweed or the usual prehistoric method of evaporation of brine at coastal locations.

Seaweed is interesting in this respect since the ashes of the burnt weed may, I think, be used as a secondary resource in the tanning process since the ash is in effect a form of impure soda ash and potash. Unfortunately I'm not a chemist and I get confused as to what is produced when this ash, K2O and Na2O and less of NaCl and KCl, is added to water.

My first question is where in the chain of producing leather from kill to finished product does salt (NaCl or KCl or the mix) fit in ? Is it at any stage essential to the process ?

My second question is the use of seaweed ash. Presumably it is its general alkaline properties that are of use in tanning ? Again, in the scheme of raw to finished product, where does the need for an alkali fit in ?

Last question, could the seaweed ash be used as a simple curative/preservative. Or more generally is salt essential when curing/preserving any fresh killed animal hide ?

Trust you can help me in this and looking forward to replies,


Mike Collins

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Focus your question a bit better please.

This response submitted by The Taxidermologist on 11/08/2002. ( )

In interior North America 1000 years ago I can guarentee salt was not a componant of routine tanning. Since the industrial revolution, it is routine in many tanneries to salt the hides to draw out moisture prior to tanning (to prevent decompostion of the hide), and also adding it to the pickle phase of tanning to prevent acid swell (the pickle phase breaks down the leather to later accept the tanning agent).

Access to salt along Ireland may have allowed it to be used in some phases of preservation of food or other items, but rubbing it in hides does not make the hide tanned. Nor does any ashes from seaweed or wood fires. The biproduct of wood ash is strongly basic, and could be used in de-hairing the hides to later make leather, but lime does not tan either.

If I've not answered the question, please re-phrase it.

Look at bit farther on th eEuropeon Cont.

This response submitted by John C on 11/08/2002. ( )

I think if you will look, you will find the Galls traded salt that was mined in the Alps. One thing that stands out is the ALPS ICE MAN clothing skins did not contain anu additional salt, just from the sweating, it was on our Discovery channel recently.

It would be doughtful that any northern langitude, enough evaporation to produce salt from sea water would be doughtful due to cool weather and lack of sunshine. However with the winds and breeze that could have been possible to use straw matting to dispurse the H2O thereby leaving the salt which could have easily been simply shaken off.

As Stephan mentioned ashes would have produced a very akaline solution, commonly know as LYE in the U.S.A. This will slip the hair rather quickly, then could have been washed out, next possibly soak in a pit with a lot of hardwood leaves, this will add tannans to the water and produce a fairly white skin. Next would have been the smoking of the hide, this adds more tannans to the hide, helping preserve it farther. On this side of the ocean Athabascan Natives in the north climates, mixed the animal brains with blood and allowed it to ferment then rubbed it into the hides. Then the hides were smoked. For hair on applications, the hides were scraped, stretched and dried on wooden hoops. Even as currently many still tan hides to thier use, oils from salmon were used to oil the hide and breaking has been accomplished with sticks and beating the the hide.

Hope this has been of some help. Many years I have watched and wondered how technolodgy work world wide without modern communications. People over the globe evolved much the same at the same times.


This response submitted by Leather Neck on 11/08/2002. ( )

There is a wealth of knowledge on this site as you see, but another source that i like to use from time to time is the American Leather Chemists Association web-site for detailed informations. Try Keyword search and the link should pop up...or under ALCA.
My good friend Dr. Waldo Kallenberger is always happy to assist with qestions on their discussion forum.
Good luck.

For Stephen (Taxidermologist)

This response submitted by Mike Collins on 11/09/2002. ( )

Thanks for your interest, you've gone some way toward clearing a few points for me.

To clarify my rambling post - are there any other methods of curing a hide apart from salting or freezing ?

For John C

This response submitted by Mike Collins on 11/09/2002. ( )

Thanks for your interest John.

I'm aware of the salt trade for these times in the Gallic areas and elsewhere but the thing is that Ireland doesn't appear to be linked into this particular bit of the trade network.

I'll check the Ice Man, thanks for that idea.

The climate was actually OK for evaporation in some areas. Even the cooler wetter areas managed to produce salt via evaporation of brine in pottery vessels...the reddened remains of the pottery and the hearths at coastal sites and around brine springs being our best evidence for this. Some mining of salt deposits occurred, notably at Hallstatt not too far from where the Iceman was found but from memory th mining at Hallstatt started a little after the time of the Iceman.

I didn't know that the ashes are the same as Lye, thanks very much for that. In the earliest Irish texts there is mention of 'sea ash' and in Scandinavia a term translated to 'black salt' which many take to mean salt produced by burning seaweeds. Surely this wouldn't be used as an alternative to table salt, being so alkaline ?

OK, back to the tanning etc. At least I know the ash might have been used in removing the hair. Apparently seaweeds generally have very little in the way of tannin inside of them so I'm beginning to think it extremely doubtful they would have been involved in any aspect of leather work/tanning. However, we have a lot of leather items preserved for prehistoric times in Ireland and all this info I'm picking up here is very useful.

Just to clarify - is an alkali solution essential in any aspect of the tanning process (or leather production for that matter) apart from in removing the hair from hides ?

Also could I ask about the smoking aspect you mentioned. Is the smoke coming from wood being burnt ? If it is, I don't get the point...what effect does the smoking have on the hide ?

Hope you don't mind these further questions.

It is interesting to learn how all our forebears lived the lives they did and as you say, we seem to have been using pretty much the same technologies and craft ways across the globe. Different ingredients here and there but much the same methods involved.

Hey Leather Neck

This response submitted by Mike Collins on 11/09/2002. ( )

I've just now found the site you gave me. Many thanks for this. I did a search of my college library today for books relating to leather work, preservation etc but they near all seem to be coming at stuff from a modern point of view. The ALCA forum will be very handy to bat a few ideas out re leather production queries for prehistoric/pre-industrial Ireland. Thanks again.

Smoking the hides --

This response submitted by The Taxidermologist on 11/11/2002. ( )

Smoking the hides serves two purposes. One, it may color the hide to a darker/natural color which would have advantages in hunters having a more camoflauge color in hunting.

Secondly, wood smoke imparts various off gases in the incomplete burning of wood. Formaldehyde is one of the biproducts of incomplete combustion of wood, and others (perhaps turpens?) all act to preserve the hide - much like smoked meats are preserved better than unsmoked meats. Also, it dries out the hide after tanning - thus preventing decompostion. In archaic times, the humidity couldn't be controlled like we do with air conditioning and dehumidifiers.

Lye & Table Salt

This response submitted by Jessica on 12/02/2002. ( )

RE: Mike Collins (For John C)

To my understanding, LYE is NOT ashes. Usable Lye can be made by running water THROUGH the ashes, this alkaline liquid is called lye. This is also a basic (traditional) step in homemade soaps, etc. Please correct me if I am mistaken.

Second of all, (various forms of) Seaweed (black salt?) IS actually used as a substitute for table salt. Most notably, it is lower in sodium than regular salt. It is also a great source of iodides, which you will notice that most table salts will also brag of. Thirdly, it provides a bit of flavor. Check out your local food Co-operative and inquire within, you can probably find it on the shelf. Happy hunting!

P.S. Great questions, and great insights and answers... mucho appreciated!

Tanning in prehistoric times (or the way I do it)

This response submitted by Monica on 12/02/2002. ( )

Hi Mike and you else,

As being one of those "Primitive Skills"-people I just thought I should add a word or two.

There are several ways preserve a hide direcly after skinning. You can either freeze it, salt it, or, most simple of them all, you can dry it. Which method you pick is of course depending on where you live. For an Inuit freezing would be the easiest way, for an African drying is easiest.
To my understanding, table salt (NaCl) has been a very rare and expensive product in prehistoric times, even for people living close to the sea. Such an expensive product could hardly be wasted in the amounts it takes to preserve a hide if there was a possibility to dry or freeze it.
Sea or table salt (NaCl) is only preserving, not tanning. "Primitive" tanning tecniques involved for instance the usage of bark (vegetable tanning), urine or different types of fat (braintanning).

Now to the ash chemistry:
The ash you get from burning wood, and probably seaweed too, consists mainly of potassium carbonate (KCO3), or potash, which chemically speaking is a salt. If potash is soaked in water it gives you lye, which has been used to make soap and also to de-hair hides. Not for tanning, though.
The de-hairing bacteria are speeded up by the alcaline environment created by the ashes. I've myself de-haired reindeer hides by smearing the flesh side with soft soap and putting it into a plastic bag.

If you are interested in the "primitive" ways of tanning hides, I can recommend where you also can order good books on the subject.

And you are welcome to ask me questions, too..

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