Glazing very thin porcelain

[Egarstang]

Attempting to glaze very thin slip cast cups. The casting slip is a commercially mixed ^6 porcelain bisqued to ^05. I’m using a commercial transparent dip glaze recommended by the supplier.  When dipped, the glaze remains completely wet on the cup and then sags and cracks off completely as it slowly dries. I know I’m in the dark without further information about the make up of either the slip or the glaze and that the real solution will be mixing my own glaze but I just wanted to make sure that I’m not getting something wrong in the mechanics of firing and application.  My first thought is that the very thin porcelain over fired in the bisque firing and is therefore not porous enough to take the glaze however it does absorb water when soaked. Would I be better off using a spray application as a starting point?
I am a newbie and very much finding my way here.

Thanks

[liambesaw]

When dipping you're relying on the bisques ability to absorb water to have the glaze stick.  If the clay becomes saturated, the glaze will not be able to stick. 

So for glazing very thin things, you may need to dip for less time, but multiple layers letting it dry between. Or what usually works for me is to glaze the interior of the vessel, and then wait for it to dry completely and then dip the outside of the vessel.

Good luck!

[Egarstang]

5 hours ago, liambesaw said:

When dipping you're relying on the bisques ability to absorb water to have the glaze stick.  If the clay becomes saturated, the glaze will not be able to stick. 

So for glazing very thin things, you may need to dip for less time, but multiple layers letting it dry between. Or what usually works for me is to glaze the interior of the vessel, and then wait for it to dry completely and then dip the outside of the vessel.

Good luck!

Thanks - will try both of those methods 

[neilestrick]

Liam nailed it. The pot has to be thick enough to take in enough water to get the desired thickness of glaze. Very thin pots can't do that. I glaze the inside the let them dry overnight before doing the outside. If the pots is super thin, it may still need more than one dip to get the job done. Do not let the piece dry completely if you're doing double dips on the same surface or the first dip may come loose. You can also try mixing your glaze thicker so it doesn't have as much water in it, but you may need to deflocculate it to get the necessary fluidity for a good application. 

[Mark C.]

glaze the insides one day outsides the next as Neil said.

[Morgan]

My mugs are paper thin and I always have to glaze the insides first and let dry overnight.

[Min]

Glazing while the pots are quite warm helps too.

[Egarstang]

Thanks everyone - I’ve tried glazing inside and outside separately and glaze appears to be adhering well.