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Testing Absorption Rate


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#1 Rockhopper

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Posted 25 May 2013 - 08:22 PM

I suspect this is one of those questions that doesn't really have just one correct answer but... I'm wondering what is the best way to determine absorption rate of a fired clay body ?

I have been working with a locally dug clay, trying to get a workable body that I can use with the ^6 glazes at the studio I go to. I've made a number of test strips, with various combinations of OM4, EPK, Flint, and Potash Spar (based on some earlier tests of the un-modified clay, and a lot of searching here and elsewhere on the web) - all of which have been bisqued at ^06, then fired again (unglazed) at the intended glaze temp of ^6. Before I start exploring glazes, I want to be sure the absorption rate is within acceptable range for functional pots (mugs, bowls, etc.)

Some articles I've found on the web say to boil the test pieces in water for 2 hours - others say to soak in a container of water for 24 hours. Soaking 24 hours in room-temperature water seems a lot simpler (and safer) than boiling for two hours - but is one method more accurate than the other ? (Obviously, the boiling option would be quicker - but I've been tinkering with this off & on since last November, so I'm not too worried about taking an extra day at this stage.)



#2 JBaymore

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Posted 25 May 2013 - 09:23 PM

More "industrial" type references for you:


http://www.ceramicin...kage-absorption


http://www.astm.org/Standards/C373.htm

http://www.ceramics.org/wp-content/.../05/sanders-capillaritye28093report-ira.pdf
best,


.................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#3 Rockhopper

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Posted 26 May 2013 - 06:48 PM

More "industrial" type references for you:


http://www.ceramicin...kage-absorption


http://www.astm.org/Standards/C373.htm

http://www.ceramics.org/wp-content/.../05/sanders-capillaritye28093report-ira.pdf
best,


.................john


Thanks John -

I've previously read the ceramicindustry.com article, and found it very informative. What I'm trying to find out now is: Is the "boil for 2hrs" method described in that article more accurate than "soak for 24hrs" mentioned in other articles - or is it just faster ?

(I guess I could try both and see if I get different results.)

#4 Min

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Posted 26 May 2013 - 10:23 PM

Absorption and porosity are 2 different things. The former can be measured by soaking, the latter by boiling. Good article to explain it better than I can in the following link. I tried his method and there was a difference in weight between a soaked only sample and a soaked and boiled sample. The procedure uses 10 mm thick by 25 mm wide by 120mm long fired test bars and a 24 hour soak and weigh, then a 5 hour boil and weigh. I don't think the size is an issue as long as the weights are accurate.

http://digitalfire.c...ramics_105.html

there are a couple more indepth articles on his site discussing this, under the Articles folder at the top of the page

Min

#5 Rockhopper

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Posted 29 May 2013 - 09:42 PM

Absorption and porosity are 2 different things. The former can be measured by soaking, the latter by boiling. Good article to explain it better than I can in the following link. I tried his method and there was a difference in weight between a soaked only sample and a soaked and boiled sample. The procedure uses 10 mm thick by 25 mm wide by 120mm long fired test bars and a 24 hour soak and weigh, then a 5 hour boil and weigh. I don't think the size is an issue as long as the weights are accurate.

http://digitalfire.c...ramics_105.html

there are a couple more indepth articles on his site discussing this, under the Articles folder at the top of the page

Min


Thanks Min. I've looked at some other articles on digitalfire, but missed this one.

Kind-of reinforces my initial suspicion that there may not be a single "best method" ... some sources say "soak 24-hours", some say "boil 2hrs" - and this one says do both and compare the results.

The one thing they all have in common is the desired range of the results.




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