General Question

srmorgan's avatar

How many coats of glazing can be put on a bisque fired vessel?

Asked by srmorgan (6738points) October 3rd, 2008

Are there any experienced potters on Fluther? I ended up with three coats of glaze on a vase and I wonder if that was too much?

Observing members: 0 Composing members: 0

9 Answers

Harp's avatar

It depends on the formulation of the glaze and the thickness of the coats.

If it’s a glaze with a high alumina content that stays put, then you should be fine; a runnier glaze will run even more in thick coats.

The total thickness of your three coats will depend on several factors: how thin the liquid glaze was, how long the bisque was immersed in the glaze (if you dipped it), and how long you allowed the piece to dry between dips (the moister the piece, the less glaze it will pick up).

You can gauge the final thickness by scratching through the glaze down to the bisque in an inconspicuous spot (you’ll be able to patch it with a dab of glaze later). Depending on the glaze formulation, you’ll want 1/16 – 1/8 total thickness. A few glazes, like oil spot glazes, can be even thicker, but even they will droop a bit during firing.

One last thing: If most of the thickness is concentrated toward the top of the piece, it will be able to handle a good bit of glaze running without gluing to the kiln shelf. But if you have a lot of thickness toward the bottom, it has nowhere to go if it runs.

If you decide that your glaze is too thick, you can always wash it off the bisque, let the bisque dry completely, and start over.

La_chica_gomela's avatar

I’m NO expert, but I think it should be fine. The only issue I would be worried about is the excess glaze running down onto the kiln, and (a) sticking the vase to the kiln floor (b) the excess glaze being permanently stuck to the kiln.

(Okay, Harp just beat me to the punch with a better answer, but i’ll press on)

If you do decide to fire it the way it is, you want to definitely use those little needly things (you know what I’m talking about?) and put it on one of the removable shelves, so if some glaze does run off it won’t be permanently stuck to your kiln.

Those are my non-expert thoughts from someone who spent two years teaching art class and running the kiln at Sunday school.

srmorgan's avatar

@Harp—
I have completed 2 five-session classes in beginning pottery here in town and started my third class last night. I hand-built a vase a few weeks ago, did some texturizing and the studio owner did the bisque firing over last weekend. So it was time to glaze the sucker.

It is about 11 inches tall and five inches in diameter and the wall is 1/4 thick.
The studio owner keeps about 40 vats of glaze available to the students and other the name of the glaze and approximate color.

First I brushed some iron and copper oxide (in one solution) on the vase,and wiped it off, A good deal of it is covered by small holes that I poked into it with the end of a pine cone!!!

I daubed some “dark green’ glaze on about 20% of the piece and brushed the same glaze all around the rim. I let it dry and my instructor told me that I should have glazed the inside first.
So I glazed the inside with :“Celadon Green” let it dry and then dipped the bottom for about 5 seconds, let that drip and dry and turned it over and dunked the other half.

What happened was that I first brushed my hand on back of the vase near the top and scratched glaze off. It looked lousy and I gave the piece a brief upside down dunk.

Ten minutes later, impatient I touched the rim and it was not quite dry and I ended up marring the finish on the rim. So I dunked the top half again.
Then I let it dry properly and moved it to the shelf where pieces are held for the next glaze firing by the owner.

So the extra glaze is all at the top. I waxed the bottom and about a 1/4 inch up from the bottom and wiped any glaze that hit the waxed area.

I am keeping my fingers crossed.

@lachicagomela, I did not realize that I could rinse the glaze off of the piece. I am going in to the studio on Saturday afternoon and I will see what some of the more experienced folks say, based on how the piece looks. That is, unless the owner by some chance began a firing today.

Everyone in my class (all amateurs except for the instructor) thinks that this is an attractive piece. Keep your fingers crossed.

Thank you both for the advice…..

SRM

Harp's avatar

Sounds like you’ll be fine. Thick glaze near the top is rarely a problem. Let us know how it turns out!

srmorgan's avatar

@harp
This afternoon I went in to the studio and the owner suggested that I wash off all of the glaze and start over.
I had used a Celadon glaze that she said did better in a thin coast when it was covering another color. I had sponged on some darker green.

I did the same things and it might be fired on Tuesday.
I will post a picture somewhere for you to see.

SRM

Harp's avatar

Cool. Exciting stuff, huh?

srmorgan's avatar

@harp

Is there a noticeable difference in the finished product (post-firing) of a piece if most of the piece was dippped in glaze and one or two spots were covered only by a layer of glaze painted on by using a brush?

SRM

Harp's avatar

It sounds like your piece has a lot of surface texture, so I doubt it will be readily apparent. You might worry if it were on a large, smooth surface.

srmorgan's avatar

Thanks…

SRM

Answer this question

Login

or

Join

to answer.

This question is in the General Section. Responses must be helpful and on-topic.

Your answer will be saved while you login or join.

Have a question? Ask Fluther!

What do you know more about?
or
Knowledge Networking @ Fluther