Hamon Clays

[Charlotte]

I got curious about the composition of the High Temperature Mortars used in hardening and creating Hamon on blades.  I had my own expectations as to what I would find based on my playing with Raku pottery processes.  

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This information is offered in good faith as typical values and not as a product   specification.  No warranty either expressed or implied, is hereby made.   Industrial hygiene and safe handling procedures are   always required.  However, each user should review the   specific context of the intended use and determine if   they are appropriate and safe. <<<<<<<<

A typical formula found from reviewing the public information in the Chemical Abstracts:

By wt/Wt %

Sodium hydroxide                           0.8-1.2%                      aka LYE

Hydrous Aluminum Silicate          40.0-50.0%                   aka Kaolin (a kind of ceramic clay)

Sodium Silicate                               40.0-50.0%      aka water glass, sodium water glass, soluble glass,

Calcium Meta-silicate                     3.0-6.0                             aka Wollastonite (used in ceramics)

Water glass is used in ordinary ceramic production in the preparation of casting slips but in a dramatically lower proportion.  The Lye is present as part of the solution containing Sodium Silicate. Calcium Meta-Silicate is, I believe, added for color and is capable of bonding with the other materials.

To the extent that you can put this material in a tube and gun it, the Sodium Silicate is responsible.

Sodium Silicate has an interesting property in that it’s shrink rate and the clay’s shrink rate are very similar.   In addition, it forms a loose net which holds together under light heating.

In my viewing of Japanese masters applying clay to their blades I had formed the conclusion that they were using a casting slip which would be consistent with the commercial High temperature mortar many people use.

[Charlotte]

excuse me please I misstated the purpose of  Calcium Meta-Silicate  AKA  Wollastonite.  It  helps reduce shrinkage and controls out gassing on firing as compared so some other materials that could be used.  Calcium Meta-Silicate is, I believe, added for color is incorrect.  I checked a second source after the post. Wollastonite is added to glazes for the same purpose to reduce shrinkage.

[BIGGUNDOCTOR]

You may want to look up wood fire clay bodies since they are upwards of cone 14+. Raku is a pretty low cone temp firing if I remember right.

[Charlotte]

You may want to look up wood fire clay bodies since they are upwards of cone 14+. Raku is a pretty low cone temp firing if I remember right.

You are absolutely correct Biggundoctor.  I mentioned my interest in Raku  solely as an introduction to my interest and the resources available to me.  The cones used in ceramics have little crossover to our heat treating as smiths;  Ceramic cones are an indicator as the slump and fold over of the time at temperature. Potters refer to this as heat work.

Kaolin. the clay in the above mixture, is a principal ingredient of porcelain  which  is often fired to cone 10 which my reference source  for a large cone gives a temperature scale of 270 deg F/hr rise to a final temp of 2377 deg F Wood fired clay bodies contain the same basic chemistry as Porcelain but in slightly different proportions and have small amounts of other compounds that give color. The information I have suggests that Wood fire clay bodies are fired to same cone range as Porcelain. 

Natural clays  are a mixture of different proportions of chemical compounds. The Japanese are famous for their Porcelain's translucent  qualities.   They are also famous for introducing Raku  to western pottery.    Raku bodies typically have some silica sand, or other grog, to help them  withstand the shock of sudden temperature change  takes them from around 1870 to open air and contact with surfaces at ambient.

The Sword Masters evidently knew how to balance all the various ingredients to prepare their recipes.  

[Frosty]

You guys are KILLING me wondering about the chemical analysis of clay when you pretty obviously haven't tried the technique. It's like a kid wanting to learn to drive by wondering about the best fuel for a top fuel dragster.

How about just mixing up some mud and trying it on a few prepared high carbon coupons? Or heaven's forbid look it up?

No wonder Steve isn't answering. If I weren't seriously ticked off in my present old coot curmudgeonly fit of pique I wouldn't just ignored this thread once again. However seeing as I haven't seen one single useful idea come up I'll just vent about the utter lack of investigative drive you guys are displaying. Seriously a REAL blacksmith would have tinkered this out in a few hours if h/she lacked imagination.

Frosty the Lucky.

[Steve Sells]

Glenn says I have to be nice. Sooooo

[Charlotte]

Ok guys just so you know.  I have my own formula for clay.  And no I'm not trying to figure it out.    I posted this because: 1) I thought it would be of interest to people that are using High temp mortars. 2.) You guys gave the same kind of Curmudgeon answers to an innocent who presumed to ask the question a while back.  The information is correct. NOTICE: I WAS VERY CAREFUL NOT TO SUGGEST A FORMULA. 

Because: 1.) For most people the standard fire place repair formulas are probably the quickest, most reliable, cheapest, most convenient  solution to the problem.

                2.) People in the this site often have to be carefully instructed before they achieve success and  since clay is  a composite material  its formulation varies widely between batches it would be impractical to give a specific formula because not every one access to a ceramic supplier a few miles down the road.  A

   As my source of refectory materials and my ceramic supplier are within an hours drive I had no reason to experiment with the Home Depot solution.  The nearest home store supplier is over 150 miles from me.  

I just reported the information I found when I wanted to see how the material I'm using compared to the High Temp Mortar.