Jump to content
Sign in to follow this  
imagodei

Opacify For Cheaper?

Recommended Posts

Hi All,

 

First post on this forum - excited to have found it.

 

I just tested out a batch of the Folk Art Guild White from John Brit's midfire glaze book.

 

It's gorgeous, but at $30 lb, the tin content is a bit expensive - any thoughts on opacifying for cheaper?

 

Does anyone use a white glaze with tin/titanium combined?

 

I've tried some other recipes with zircopax and I much prefer the creamy white of tin over the bright bluish white of the zirc. 

 

Folk Art Guild White  ^6 F-4 Feldspar 18 Spodumene 10 Silica 18 EPK 18 Dolomite 18 GB 18 Tin 13 RIO 2 Bentonite 2

 

-Vanessa

 

Share this post


Link to post
Share on other sites

13% Tin seems really excessive. Are you sure you're reading that right? I would run some tests reducing that number and see how low you can go and still get the look you want. It could be that having it that high is doing something more than just opacifying, though. You can usually get quite opaque with 5-6%. Barring that, you'll have to use a zircon opacifier, which will take twice as much but still comes out cheaper.

Share this post


Link to post
Share on other sites

Thanks for your feedback Neil!

 

It was definitely 13, I found slightly variant recipes elsewhere online, and all had a similar amount of tin. I'll try as you suggest and go lower to see if I can get the effect I want with less Tin. 

 

I'm also going to test out how many grams of glaze it takes to cover an average sized pot - because maybe the price won't be as bad as the $30/lb sticker shock.

 

Can Tin and Zircon opacifiers be used together with any success? I know i can test it myself, but if there's some known weird interaction I won't bother with it.

 

-Vanessa

Share this post


Link to post
Share on other sites

I've done some recent tests blending tin, zircopax and titanium. Watch the titanium levels: it can be a bit silvery and pretty mixed with other things in smaller quantities, but if you get too heavy handed with it, you find yourself with some unintentional floating blue type glazes, especially if you've got Gerstley Borate in there. That, or it can go yellowish.

Share this post


Link to post
Share on other sites

You can get tin oxide from US Pigment for about $22 a pound. 13% in a 9000 gram batch (5 gallon bucket) will need about 2.5 pounds, about $57 worth of tin. That probably triples the cost of the base glaze. It's expensive as glazes go, however it's only about $2 per pint, which is cheap compared to commercial glazes, and only a few cents per pot.

Share this post


Link to post
Share on other sites
Guest JBaymore

The zirconium variations of opacifiers give a "cold" white.  Tin gives a "warm" white.  Just the way it works.

 

best,

 

..............john

Share this post


Link to post
Share on other sites

Thanks for all of the thoughtful responses!

 

@marc I'm going to give the 50/50 a shot! I'll report back the results.

 

@Diesel It's funny you say that, i just tested removing the colorants from a titanium base glaze and it was surprisingly yellowy with streaks of blue! Not what I was expecting, but now I understand why the added cobalt was going green where thin!

 

@neil if I found this glaze at the store I'd buy it for $2 a pint...so I guess that puts it in perspective :)

 

@john, I just wish the price difference between the two weren't so stark! 😭

 

For reference, I've attached a pic of the glaze

Share this post


Link to post
Share on other sites

I suggest  a test using 1/2 the tin an 1/2 with zircopax as a starting point.I did a lot of this testing in the early 70s with a glaze that used lots of tin. The 50/50 worked well in the end.

That can also cut chromium flashing, sometimes desirable, and more often not desirable.

 

best,

Pres

Share this post


Link to post
Share on other sites

I was testing on cylinders 3.5 inches high, 4" diameter, so roughly 100 sq inches in glazes surface area.

 

100x.15=15g

 

So, per Neil's calculations at $.006 per gram, that's about 10 cents. I guess it's pretty nominal.

Share this post


Link to post
Share on other sites

I messed around with that recipe with the tin levels. Don't have my notes in front of me but I think I got it down to around 9 and it still made a nice white. If you replace too much tin with zircopax you loose the rusty colour where the glaze breaks on edges. A bigger problem was finding an iron oxide that doesn't produce speckles in the glaze. (unless that is what you are looking for) I would do a couple line blends or triaxial blends to get the white the way you want it. Easy way to get a lot of glaze tests done with mixing up only a few glazes. On your pot I'm not seeing the rusty breaking colour, the iron makes a difference in that. You can get a really nice white breaking rusty red with the right iron.

 

edit: JosephF on these forums has done a fair bit of testing with that glaze also, hopefully he will chime in here also

Share this post


Link to post
Share on other sites

@mark, yes, good idea to do more than just the 50/50

 

@cambria - thanks for sharing that resource, just joined the group on Facebook! To think I didn't know about either of these resources a couple weeks ago!

 

@marcia, I will try reducing it and cutting in zircopax before committing to the 13%, but at least from the calculations, I don't feel so bad about the price per pot.

 

@min, thanks for the 9% rec, I'll try that and a few other variations of tin levels. The rust breaking is there, and he subtlety of that is one of the things I love about this glaze! I don't have any speckles, but I saw that in other picture online of the glaze. I'm glad to have the iron I have in that case!

 

Thanks everyone!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.