Stephen Hill Fake Ash midrange oxy glaze pinholes needhelp

[Potterbabe]

Firing this at cone 5.  Firing this at cone 6.  Firing this at hot cone 7.  Always a slow cool kiln.  Always pinholes.   Test tile always look good.  Help!

Stephen Hill Copper Ash

whiting  32.5%

silica  6

Epk 24.7

Dolomite  2.8

frit 3124   14.9

Albany Slip  19.1

Copper Carb  5.6

Bentonite 2

 

[neilestrick]

What clay body are you using?

[Callie Beller Diesel]

How thick is the application?

[Potterbabe]

I’m using Laguna WC 613 and my application is a single quick dip SG 1.5.  Strange my test tiles never shoe pin holes.  Again I have a slow cool glaze schedule.  I’ve tried damp wiping the bisque.  I mechanically trim and make sure I metal rib the surface smooth.

I am glazing pots with another glaze and where it overlaps there are no pinholes.  Looking at similar glazes most have lithium no unavailable.  If there’s a like looking glaze out there I’d love the recipe.

[Potterbabe]

[Mark C.]

darker clays usually equal more glaze issues 

are you running the glaze thru a 80 mesh sieve ?

Are you firing very slowly at the end of the fire going thru the glaze melt period????

I think the pits are not  forming in the cooling cycle but the heating cycle -slow it down near the end of the melt period

[Min]

Loss on Ignition (LOI) with this glaze is going to be extremely high given the huge amount of calcium carb in the recipe. I would add a drop and hold/soak to help the pinholes heal over plus a slow rise for the last 200F of about 100F / hour. Dropping 100F then soaking for 20 minutes would be somewhere to start for the drop and hold.
 

BTW are you using this glaze on surfaces with food contact? It isn’t going to be very durable given the very low silica in the formula. Might taste the copper with acidic foods. Alberta Slip subbed for the Albany?