Old Amaco glaze? Solidifying on the bottom of the bucket.

[Syvanis]

Hello, 

As mentioned in my last post I am a Teacher that was put into a brand new position 4 days before school started. My back ground in clay is minimal and I am learning a TON, but having some specific issues. The history of my classroom was a very experienced ceramicist ran the program for 25 years. She was replaced by a person that ...kept things very simple... I want to give my students a wide range of potential projects. 

There are about 15 AMACO 5 gallon glaze buckets. Talking with students it seems for the last 5 years the teacher never did dip glazing with the students and always did underglazing.  Maybe I am wrong but it seems like dip glazing is more typical for the average potter. Anyway. I decided to use the dip glaze. We did a successful fire and most of them turned out. 

Two colors gave me issue. Arctic Blue and Nite Black both seemed to collect very heavily on the bottom of the bucket. Specifically the Nite Black even after going at it with a drill and mixer for 5 minutes still was not mixing well.  

I thought I had got the Arctic Blue well enough, but everything that was glazed with that color had little to no blue afterwards. Black I stopped kids from using as it felt like it wouldn't work.

SO Does glaze "go bad" If it sits and collects for years it is better to just let it go? What can I do to mix that better? Is it just a matter of running the drill through it for longer?

Last time this forum was a ton of help and thanks for any answers!

[Callie Beller Diesel]

The good news is that no, glazes don't go bad. They're a combination of a few different minerals, and as long as they're thoroughly mixed, they should be able to be used almost indefinitely.  The thing is though, you have to get all the heavy stuff off the bottom, and all the lumps out, or you're not working with the full recipe. If you have a significant portion of the ingredients still on the bottom of the bucket, it will affect the outcome of the glaze. If they've been sitting for a few years with no mixing, glazes will settle and hardpan. Some glazes will do this worse than others, as you've discovered with your Nite Black and Arctic Blue. If the glazes have ever been stored outside somewhere where they'd have frozen and thawed, that would have made the situation even worse.

I used to have to deal with a lot of frozen glazes before I had a heated studio, and I found a large kitchen whisk to be more effective at re-mixing solidly hardpanned glazes than a drill with a paint mixing bit. I think that the high velocity of the drill actually compacted things more. It will still be a long, messy job to stir it up, and it would be a good idea to run the glazes through a sieve after you get them stirred. It'll distribute the glaze ingredients more thoroughly. You may find that the water levels in the glazes have changed from the optimal if they've been sitting a long time, but try not to add water to anything until you've got it de-lumped. If the glaze seems overly thick, add water in small quantities and mix thoroughly before checking the consistency again. 

Would the old pottery-proficient teacher be available for a consult, by any chance?

[Syvanis]

Sadly no. She was not well treated and unfortunately "Took her ball and left". I tried communicating with her and she said the school wasn't going to get anything from her. It wasn't anything to do with me, but years of mistreatment by the administration. 

Thanks for your advice I will work it harder! I do have a large sieve so I will use that after really going at it. 

 

 

[Min]

Some glazes need a flocculant to keep them suspended. One that is easy to find at grocery or drug stores is epsom salts. Stir as much epsom salts into a cup or so of very hot water until no more will dissolve then stir in a teaspoon of this saturated epsom salts solution at a time until the glaze won't settle. Rough ball park figure is about 1 tsp of epsom salts solution to 1 gallon of glaze. 

If the glaze is just stuck on the bottom and being stubborn and not budging then dumping the water into a second bucket and using a loop tool to cut and scoop out the glaze works well. Stir a bit of epsom salts into the water you put in the second bucket and start stirring in the solids. 

I don't know what is in the Amaco glazes but if they used stains for the colourants those could very well be sitting in the bottom of the bucket as stains are one of the heavier materials we use. Get your students to get in the habit of stirring up the glazes well while using them, not just at the beginning of class. A toilet cleaning brush works well for this, they are inexpensive so you could keep one per bucket of glaze so they don't have to be washed out after class.

[Syvanis]

Yes we were mixing up before each dip. And only those two didn't seem to work well. I keep telling the kids my plan is to be one step ahead of them and I am learning as much as them.

 

 

[Chilly]

20 hours ago, Callie Beller Diesel said:

run the glazes through a sieve after you get them stirred. It'll distribute the glaze ingredients more thoroughly

 And pour from bucket to bucket 3 or 4 times .  It mixes better than stirring.