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Rockhopper

Member Since 16 Dec 2012
Offline Last Active Today, 07:18 PM
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Topics I've Started

Glaze From Local Creek Clay - What To Add ?

28 December 2016 - 08:57 PM

A couple of years ago, I was trying to develop a workable ^6 clay body, starting with clay I dug from a nearby creek, and several forum members contributed valuable suggestions to that project.  After a lot of trial and (mostly) error, including a couple that completely melted in the kiln, I was able to make a few flower pots that now hold plants in my office - but never really found a blend that was 'friendly' to work with, and wound up setting the buckets aside to pursue other things.

 

I now have some time to re-visit my creek clay - and decided to take a different approach:  I want to see if I can develop it into a glaze.

 

As a starting point, I made some slip, and applied a coating to the inside of a small bowl - and fired at ^5-ish.  (^6 on the sitter gives me a near perfect bend on a #5 self-supporting cone, with slight bending on a 6.)

 

The result is a light cream/butter color, but with the texture of 200-grit sandpaper.  And, as could probably be predicted by the texture, is very porous.  Obviously not something I can use on a mug or bowl that's going to be handled.

 

So...  I'm once again reaching out to those that have been down this road before me, and asking for suggestions: 

 

What would you add, and in what proportions, to turn this into a "glassier" glaze.  (I wouldn't mind if it winds up being a matte finish - but I need to get it smoother, and less absorbent than the clay it's applied to.)

 

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Highwater Speckled Brownstone Vs Standard 112 ?

28 December 2016 - 08:12 PM

Would like to hear from folks who have used both of these clays, as-to how similar (or different) they are, and whether you have/had a strong preference for one or the other.

 

The technical spec's on the respective websites indicate the 112 shrinks 12.5% at ^6, with 2.5% absorption - and the Highwater says it shrinks 10% at ^6 with < 1% absorption.

 

The pictures indicate they are very similar in color but, if the above numbers are accurate, there are obviously some differences in formulation.  The shrinkage difference isn't really a big deal to me - don't care a whole lot whether a bowl that stars out 10" across winds up at 8.75" or 9" - but it seems like that's a pretty significant difference in absorption.

 

I've been using Standard's 112, because I was given several boxes that had dried out after being abandoned by former students at a nearby studio.  My local supplier stocks both, so I am thinking about trying the Highwater, because of the (apparently) much better absorption - which I'm thinking might be a better choice for vases & other pieces intended to hold liquids.

 

I realize the only way I'll know for sure is to buy a box & try it for myself - but I'm curious to know:

 

> Did you find one noticeably easier than the other to throw with ?

 

> What about glazing ?  Is one more/less prone to fit or other glaze issues ? (So-far, I'm using mostly Amaco PC glazes.)

 

 


^5 On Sitter Bent To 90* - But ^5 On Shelf Barely Started Bending

04 September 2016 - 10:22 PM

Just finished my first glaze firing in a manual/kiln-sitter electric kiln.  Everything went fairly well, except that it appears to have under-fired.

 

Used a 5, centered on the sitter, and self-supporting 5 & 6 near the center of each shelf. (3 shelves)  The sitter cone seems to be bent correctly, to approx. 90*,  but there is almost no bending in any of the witness cones, and some of the glazes are nowhere close to the expected colors.  (Various PC glazes.)

 

Is it unusual for the sitter to register a full cone higher than the rest of the kiln ? Based on the #5's just barely starting to bend, I'm guessing I pretty-much fired to ^4.  (and wishing I had put 4-5-6 instead of just 5-6 on the shelves, so I wouldn't have to guess).

 

I'm considering re-firing the same load, with a 6 on the sitter - but not sure whether that's a good idea, or if I should wait 'til I have some more stuff ready to fire.

 

Would appreciate any insights from those that have already been down this path.