Jump to content
Sign in to follow this  
glazenerd

Coma Clay

Recommended Posts

I have been working for several years trying to formulate a clay body for tile work, but even more so conducive to crystalline glaze.

The criteria being:

1. Stayed flat when forming. Once I cut it, I do not touch it again until bisque. No flipping, no weighting, etc. DONE!

2. Raise the COE to get closer to crystalline glaze. (not there, but much closer.) Use to get elongated concentric linear cracks.

3. Formulate to encourage crystal growth. DONE!

 

Coma Clay 01

 

 

The top tile is iron fired to cone 10 with a total 2.5 hours of soak.  (1 5/8" max. crystal size)

The bottom tile is copper fired to cone 6 with 2.5 hours of soak.   ( 2 1/4 " max. crystal size)

Cone 10 is used by most potters firing this glaze because it produces larger crystals: that is no longer the case.

 

Nerd

 

Note: all crystalline glaze has a crackle effect COE, nature of the beast.

Share this post


Link to post
Share on other sites

Actually Pug, I call the crystals "florets". we have the same eye.

 

Marcia: I gave it the name "coma", because the clay has no memory. 0.18% MGO, 0.31 FE.. ultra white at bisque/maturity.

 

Joseph, few more tweaks, then I am going to set my sights on bright red in oxidation.  Have some ideas :)

 

Nerd

JBaymore likes this

Share this post


Link to post
Share on other sites

Joel

Sodium actually. Pearl Ash was used in part. very high COE but has to be titrated due to high PH>

Some sodium in cone 10 is acceptable because the additional heat disassociates it more so.

This clay and glaze each have less than 0.15% batch weight of sodium. It has been the standard that sodium is acceptable in glaze, but I have found that to be a myth for cone 6. If you look right off the tip of the lowest crystal in the iron tile you will see faint-thready crystal formations. In my testing, these are sodium crystal forming: both potassium and sodium will form crystals.

Nerd

Share this post


Link to post
Share on other sites

Tests results as of 8-14-16. After some minor tweaking of the Coma Clay formula- noted as formula T10. The large tile on bottom is Laguna Porc. ^9, and the round tile on top is Coma Clay T10.   Both have identical glaze formulations and colorant percentages: both had a total of 2.5 hours of soak holds. Coma T10 peak 2228F (5m hold)

Coma T10 crystal size 2.5", Laguna porc. ^9  crystal size 1.75:. Note also that the COE crazing issues have been resolved.

 

ComaT10

 

 

Well, that only took 7 years to figure out. The other note of interest, critical part of crystalline glaze is application rate :Coma T10 0.40grams per Sq. Inch. Laguna porc ^9 is 0.65 grams per sq. inch.

 

Nerd

 

Neodymium (rare earth)

5NeoFe010

Pugaboo and LeeU like this

Share this post


Link to post
Share on other sites

 

 

Marcia: I gave it the name "coma", because the clay has no memory. 0.18% MGO, 0.31 FE.. ultra white at bisque/maturity.

 

:)

 

Nerd

 

 

Coma clay...........If  you fired it beyond the point of vitrification ,, you call it "Coma-toast".    .......just a thought. :D

 

All kidding aside, it looks great.

glazenerd likes this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×