Tag: witness

A long day getting ready

~ Sebastian ~ 2 Comments

First thing to test is the kiln. If it is over firing or some other malfunction is going on its of no use to be even attempting to make a base glaze. Sarah from Olympic Kilns gave me a few cones to test with. I’ll place on each shelf so we can see if we are getting even heating from top to bottom. One thing I noticed in the last firing was that the click to turn on the elements stayed on longer than I heard it before. Almost a full 60 seconds. I don’t know if that has anything to do with it, but we’ll see.

I keep notes of glaze tests that I’ve done in the past but got a great tip from Jason and Megan at Stone Mountain Clay and Glaze – Keep a firing log and record the times that it takes to reach temperature and I suppose its good protocol to record the cooling times to room temperature as well. This will tell you if your elements are going bad or a thermocouple or something like that. Or maybe in my case if it runs very short and over-firing we’ll know by the time it is supposed to take to reach temperature. I’m trying to eliminate as many variables as possible as is standard in just about every type of troubleshooting.

Also on order and will be here shortly:

Amaco Hydrometer – for measuring and keeping a consistent glaze density

The range for dipping or pouring glazes is 0.9 to 1.00.

The range for spraying glazes is 1.5 to 1.7.

The range for brushing glazes is 2.2-2.5.

Kemper DTA Glaze Dipping Tongs – Because I’m tired of brushing on glaze and getting inconsistent applications.

Aftosa Wax Resist – For creating a more precise glaze line on the feet of my pots.

Stainless 8 Inch Caliper – I really really want to get into making lidded vessels.

Ozeri Pronto Digital Scale – Need precise measurements for each ingredient (duh!)

 

For those interested in the base glaze recipe that I intend to match to my white clay body

Recipe – Plainsman Cone 6 M370 Transparent Liner Base

Material Amount Units +/- *Stat
Nepheline Syenite 18.30 kg
Ferro Frit 3134 25.40 kg
EPK 19.60 kg
Wollastonite 6.90 kg
Silica 37.60 kg
Talc 2.30 kg
110.10

 

Witness Cones 5, 6 &7 to see where it ends up at and where in the kiln.
Respirator, because I like to breathe and want to continue to breath even after mixing dusty chemicals.

 

Christmas part 2! 5 lbs each of a bunch of chemicals.
Broken scale – new one on the way from Amazon!

 

Celebrating Failure

~ Sebastian ~ Leave a comment

Pretty much everything that could have gone wrong with this last firing has gone wrong.

Clay body cracks
Crazing
OLYMPUS DIGITAL CAMERA
Crazing reduces the strength of the vessel by up to 80% A short drop to the wooden floor split this right in half.
Blistering AND crazing
Blistering
Blistering
Pinholing AND Blistering
Pinholing like a CHAMP!
Even a bit of reduction in part of the kiln. Although I must say the reduction looks beautiful!

I’m picking up some dry materials to start testing my base glazes. At least I know that my chosen clay body tolerates overfiring very well.

I’m getting some witness cones (5, 6 and 7) to stack on each shelf and see what they do. I don’t understand whats happening yet. Olympic says that the kiln usually underfires if something is wrong rather than overfiring. The company that makes my clay body says that blistering happens from overfiring. The cones should tell the tale though. I need to get that straight before I drive myself crazier than usual.