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lowering a glaze's melting point

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Long time not see you guys in this forum. Why you should lower the glaze cone 5? If you want the melting point for cone 021, you can just use low glazes. May be for lowering that point is too extreme. More effected just 5-8 cones lower such as cone 5 to cone 03. Sorry guys, I need input too if my comment was not correct.. :rolleyes:

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Guest JBaymore

While making "glazes" at 021 is likely just barely possible......... they would usually be called something like overglaze enamels or china paints here in the west........ to take a glaze formula that exhibits certain characteristics at cone 5 and try to move it down to cone 021 and retain those same characteristics is likely neigh on impossible.


At 021 .............. you are even below the typical china paint range... of about 017. Such a "glaze" would be very unstable and "soft".


Please post the formula or recipe that you are wanting to change. Also what is the rationalle for the drastic firing end point heat-work reduction?





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  • 6 years later...


A couple ways to lower the glaze melting point is less silica and alumina, more flux,  and probably an easy way is Boron. Matt Katz derived a fairly linear relationship for cone temperatures and Boron in a a recipe under UMF. I often use it as a predictor if I desire a recipe to have more movement and melt earlier.

the screenshot below depicts a recipe I wanted to melt a bit earlier, say cone 4.5 ish so I raised the Boron to about 0.20 to achieve the look and performance I was seeking. The basic Boron bench marks under Katz’ research (+/- 10%) are :

  • none at cone ten
  • 0.15 at cone six
  • 0.45 at cone 04

He has  a spreadsheet on his website free for distribution or you can easily plug your recipe in at  glazy.org and adjust your Boron by varying the Gerstley or Gillespie or Fritt as necessary. If that all sounds mysterious then a little research will help you a lot. In the end, the basics are pretty straight forward. The chemistry approach is what I find easiest for me but there are many valid ways of learning including a lifetime of trial and error. As with everything in clay, firing and confirming are absolutely essential to confirm your design performs as you intended.


Edited by Bill Kielb
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If you have access to glaze

On 3/24/2019 at 1:01 PM, dpgolias said:

How would you lower cone 5 glaze to cone 3?    Just add flux?

If you have access to, and understand glaze calc software, making adjustments to the unity formula would be the way to go, with increasing one or more of your fluxes, or decreasing the alumina and silica. If you're working off the recipe, then the easiest way to go would be to add/increase the frit or Gerstley borate. It may take as little as 3% to drop it 2 cones.

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