How can you decrease the density of the crazing cracks?

[Kathryn Howlett]

I have a commercial crackle glaze which makes a very dense crackle pattern.

Is there any way to decrease the density of the crackle pattern to make it

look more like a Raku pattern? 

[Min]

Not too confident it would be sufficient to take a heavily crazed glaze into one that is a lot less crazed but what you could try is adding some silica to it.

There isn't always "room" in a formula to dissolve more silica but if the glaze is able to then this will reduce crazing. Given we don't have the recipe it's going to be all trial and error as to how much the crazing will be reduced and if the glaze is able to dissolve it.

Is the glaze a brushing glaze or dry glaze that is made into a dipping glaze? Either way I would suggest drying out some of the glaze and weigh out 100 grams of it. To this add 5 grams of silica, then reconstitute and sieve the glaze. Apply it to a test tile then add another 2.5 grams of silica, sieve and apply to another test tile. Repeat one more time with another 2.5 grams of silica. This test isn't very accurate since each time you are applying the glaze you are removing some of the inital 100 grams but it should give you somewhere to start.

edit: have you tried the glaze on a different claybody?  Crazing or non-crazing is a glaze fit issue with the claybody.

[Kathryn Howlett]

I have my own brush on commercial glazes and the studio has dipping glazes. I also have a bag of dry glaze that I can experiment with. It was another studios left over giveaway freebie and  I don’t know the ingredients, but it is a white gloss glaze. 

[neilestrick]

The crackle pattern gets larger as the glaze gets closer to fitting the clay. Adding equal parts silica and kaolin (by weight) will generally help with glaze fit, although with premixed glazes it's hard to know just how much to add since you don't know how much actual glaze material is in the container.

[Callie Beller Diesel]

Adjusting bottled glazes is tricky, because in addition to not knowing what’s in the recipe to start with, they add gums and brushing agents that change how a glaze dries. Adding material can affect how well those things work, because you’re diluting them. Some commercial dry glazes will have them, some won’t. Usually if a manufacturer doesn’t recommend sieving or recommends minimal mixing, or specifies the amount of water to use, there’s some suspension agents or gum of some kind. 

This is not me trying to dissuade you, it’s only things to keep in mind as you test. All things are possible if you have the time and energy to figure it out. It will just be easier to adjust a dry base glaze from Plainsman (who provides the recipes of their base glazes) than a bottle of Mayco.