How to make a gloss glaze more glossy?

[katkat1000]

Hi! I'm very very very new to mixing my own glazes and I was wondering if anybody who has more experience would know how to adjust this cone 6 clear gloss glaze to be more glossy? This recipe fires well with my clay body (Georgie's Kristy Lombard or G-Mix 6) and Amaco underglazes, but I just wish it had a bit more sheen to it. 

Here it is: 

Feldspar Custer 200m - 36.5%, Frit Ferro 3134 - 20%, EPK - 18%, Silica 400 - 12%, Whiting - 8.5%, Talc 325 - 5%, Bentonite -  2%

 

 

[Bill Kielb]

Hmm, this one is tough as it is fairly glossy at this point. First thing is you very likely do not need the bentonite as you have 18% clay which should suspend things. Since bentonite really does not contribute to the look, I would remove it if not absolutely needed.

Boron is a bit  high in this recipe. More ideal would be about 14% 3134, which actually may improve the gloss a bit strangely enough.

The other technique would be to move the Si:Al ratio by adding or subtracting a little silica. 7:1 is in theory the glossiest but that is not written in stone so increasing silica slightly often can improve the gloss. In your case this glaze is already slightly higher than 7:1 so increasing by 10% may improve it. If not it would be worth decreasing it by 10% which may also improve it.

So I would run a test with the reduced 3134 to see what effect it has. If it improves, then changes in the silica level may improve it further.

All of these composition changes may affect the fit as well, so it’s possible this could end up with more gloss and no longer fit your clay body so testing is super important.

Finally we ought to be sure it was fired to maturity, do you use cones, can you post a picture?

zlastly, this is a clear glaze, Sue MCCleod has a great article on making your clear glaze as best you can. Those same tests will affect the gloss level and could provide some insight on adjusting this for highest gloss. https://suemcleodceramics.com/getting-clarity-with-clear-glazes/

[Min]

If it isn't glossy enough when fired to a full cone 6 then I'ld run some test tile tests with increasing silica. Mix up 200 grams of the base the way it is now, I agree with Bill in that you can probably skip the bentonite. Mix and sieve the test batch then dip a test tile, this is your base line gloss to judge the rest of the test tiles with. Now add 3 silica, remix and dip another test tile. Keep repeating this addition of 3 grams of silica until you get up to a total of 5 additions of 3 silica. (Base is 200 so each silica addition is adding 1.5% silica.) Fire the test tiles to a full cone 6 then compare gloss levels. Towards the upper amounts of the silica additions the glaze might look underfired and rough looking, this is when the glaze can't take that amount of silica into the melt. 

[BobMagnuson]

You might also try dropping the talc.  It is unlikely that magnesium is an active flux at cone 6 and probably is acting as a matting agent.  Of course this could also affect the fit, so further experiments may be needed, as Bill and Min have described.

[GEP]

I might look glossier just by applying it thicker. Dip a test tile into the glaze, then dip the top half only of the tile a second time. If the second dip make the surface shinier, then you can either use double dips when glazing, or adjust the water amount to make the glaze thicker. 

[Callie Beller Diesel]

Something I’m wondering is if the glaze isn’t as glossy as you’d like it because there’s micro bubbles in it.

IF this is the case, you could also try adjusting your firing cycle. To get rid of them, or minimize them as much as possible anyway, you can add a drop and soak to the end of your firing cycle if you’re not using one already. If the bubbles are more concentrated over areas with certain underglazes, try applying those underglazes before the bisque. 

Last step in this troubleshooting line would be to look to your bisque firing cycle, although this is something that tends to be more of a concern with darker clays. The principle holds though. Hotter bisque isn’t always necessary, but a longer one that allows all the chemical organics to break down properly and escape is what you want.

[katkat1000]

Thank you guys so much! This was so insanely helpful. Dang, now I can't wait for my testers for this to come out of the bisque so I can try all of these adjustments.

[Bill Kielb]

5 hours ago, katkat1000 said:

now I can't wait for my testers for this to come out of the bisque so I can try all of these adjustments.

Since you appear to enjoy, here is a recipe that we use for a very glossy finish. No guarantees and glazes often behave and fit very differently for folks but it was named hard candy clear because of its gloss.

nephy sy - 21.88, silica - 23.44, Gerstley borate - 15.62,  epk - 20.32, wollastonite 18.75

again, definitely test first, but it has worked well for us, anyway Best of luck!