Jump to content


Photo

Glaze percentages


  • Please log in to reply
8 replies to this topic

#1 Alina Albu

Alina Albu

    Member

  • Members
  • PipPip
  • 25 posts
  • LocationPortugal

Posted 17 May 2013 - 06:34 AM

Hello there

I have this handwritten glaze recipe where the ingredients are correct, but the percentages don't seem to add up to 100 for the main body. It is possible i made a mistake when I jotted them down. I don't have time to test, can anyone suggest what I could do to fix it?Does it need fixing or is it possible it's ok the way it is? Shall I use less dolomite?Like 12%?

Sodium Feldspar 85%
Dolomite 15%
Bentonite 3%
Add:
Rutile 6%
Cobalt 0.4&


Any help, much appreciated

Alina

#2 Marcia Selsor

Marcia Selsor

    Professor Emerita, Montana State University-Billings

  • Members
  • PipPipPip
  • 3,826 posts
  • Locationwhere Texas, Matamoros, Rio Grande and Gulf of Mexico come together.

Posted 17 May 2013 - 07:50 AM

If you move the bentonite down to the "add" part, it works.
The bentonite is used as an additive to help with the glaze suspension.
Marcia

#3 OffCenter

OffCenter

    Advanced Member

  • Members
  • PipPipPip
  • 1,372 posts

Posted 17 May 2013 - 09:08 AM

Hello there

I have this handwritten glaze recipe where the ingredients are correct, but the percentages don't seem to add up to 100 for the main body. It is possible i made a mistake when I jotted them down. I don't have time to test, can anyone suggest what I could do to fix it?Does it need fixing or is it possible it's ok the way it is? Shall I use less dolomite?Like 12%?

Sodium Feldspar 85%
Dolomite 15%
Bentonite 3%
Add:
Rutile 6%
Cobalt 0.4&


Any help, much appreciated

Alina


Marcia has already solved the problem, but do you really intend to use this glaze without testing it first?

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#4 TJR

TJR

    Advanced Member

  • Members
  • PipPipPip
  • 1,197 posts
  • LocationCanada

Posted 17 May 2013 - 09:26 AM

Marcia is correct. Your glaze does add up to 100%
Bentonite keeps the glaze from settling as you have no clay in your glaze.
I agree with Jim. Put this glaze on a verticle test tile to see if it runs. Runny glazes ruin kiln shelves. Just sayin.
TJR.

#5 Alina Albu

Alina Albu

    Member

  • Members
  • PipPip
  • 25 posts
  • LocationPortugal

Posted 17 May 2013 - 01:27 PM

Aaaaah, now that makes sense - Thank you Marcia. I must say I did not think that about Bentonite. We live and learn.

Jim and TJR - I have used the glaze before, it was at another potter's studio, she dictated the recipe to me (hence my thinking I made a mistake). It is a nice kind of sky blue glaze, glossy, I like it on all bodies ~but will have to test it on my new black clay.

However, it does tend to "spit" a teeny little bit, not quite sure why. My guess is that it happened when I laid it on a bit thick. Anyway, thanks again. Problem solved.

Alina

#6 Mark C.

Mark C.

    Advanced Member

  • Members
  • PipPipPip
  • 2,731 posts
  • LocationNear Arcata Ca-redwood rain forest

Posted 17 May 2013 - 01:48 PM

On another note some of my glaze formula do not add up to 100% always and work just fine.
You should also jot down (next to recipe) what cone this glaze is for so you always know the firing range in the future.
Mark
Mark Cortright
www.liscomhillpottery.com

#7 mregecko

mregecko

    Potteries

  • Members
  • PipPipPip
  • 153 posts
  • LocationBay Area, CA

Posted 17 May 2013 - 02:06 PM

Also worth asking... Cobalt Oxide or Cobalt Carbonate? One has approximately double the actual cobalt basic oxide of the other, so will affect the intensity of the blue you get.

An online glaze simulator tells me this is a pretty high-fire glaze (http://www.glazesimu...m/recWizard.php).... Just curious, what are you firing this at?

#8 Alina Albu

Alina Albu

    Member

  • Members
  • PipPip
  • 25 posts
  • LocationPortugal

Posted 17 May 2013 - 04:42 PM

Also worth asking... Cobalt Oxide or Cobalt Carbonate? One has approximately double the actual cobalt basic oxide of the other, so will affect the intensity of the blue you get.

An online glaze simulator tells me this is a pretty high-fire glaze (http://www.glazesimu...m/recWizard.php).... Just curious, what are you firing this at?


Hi mregecko

Oxide.

I am not familiar with cones, I fire at 1255ºC with a 20 min soak and it works beautifully for me. Tried the glazesimulator, don't agree with above cone ten - is there anything above cone ten?! This is a glaze that has been used by other potters I know for this range of temp.

Sometimes these things are too clever for their own good.(:-)

Have a great weekend!

#9 mregecko

mregecko

    Potteries

  • Members
  • PipPipPip
  • 153 posts
  • LocationBay Area, CA

Posted 17 May 2013 - 05:25 PM

Hi mregecko

Oxide.

I am not familiar with cones, I fire at 1255ºC with a 20 min soak and it works beautifully for me. Tried the glazesimulator, don't agree with above cone ten - is there anything above cone ten?! This is a glaze that has been used by other potters I know for this range of temp.

Sometimes these things are too clever for their own good.(:-)

Have a great weekend!


1255 is a mid fire, around cone 6-ish (Depending on what cone system you use, ramp, soak, etc).

And the glaze simulator isn't infallible, I'm sure there are better ones out there! Just a quick check :-)

Glad you got the answers you needed!

-- M

PS: Yes, there are definitely cones over 10. They're usually reached with fuel-kilns instead of electric.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users