How to make this glaze a bit less glossy?

[Bam2015]

Hello All & Happy Holidays!

I would like to make the following glaze a bit less glossy. It works great on my clay body, so I'd prefer to try to tweak this recipe rather than start with a new less glossy recipe. Any input would be appreciated.

EPK                        20.00

Ferro 3134        20.00

G-200                   20.00

Silica                     19.00

Wollastonite    15.00

Talc                            6.00

 

Thanks, 

Betty

[Min]

How comfortable are you working with glaze chemistry? 

This is one of those questions that can have vastly different levels of complexity in the answering.

Also, are you using G-200 spar or a different feldspar now that the original G-200 is no longer available?

[Bam2015]

Min,  just slightly comfortable with glaze chemistry. I have about 3 gallons of the recipe I posted. I bought it mixed from a pottery studio.  

I mixed up four different clear glaze recipes & tested them, but will stick with the recipe which I posted. I have the raw materials to mix the recipe and feel comfortable mixing it, but I have Custer & Minspar feldspar. 

I was hoping to tweak the already mixed 3 gallons to make it less glossy. Maybe I should start with a new recipe using either Custer and/or Minspar first and test that? If I like that then how would I make it less glossy? 

Maybe I'm just getting in over my head.

Betty

 

[dhPotter]

Of the 2, Custer and Minspar, Custer is a better replacement for the G-200.

Custer is closer to the same chemistry as G-200. 

[Min]

@dhPotter, newer analysis of Custer has fluxes a fair bit different, might be an idea to update your materials data field if you get a new supply of it. Link below to a thread with updated new analysis. Could save some shelf grinding with runnier glazes. 

 

[Min]

8 hours ago, Bam2015 said:

Maybe I should start with a new recipe using either Custer and/or Minspar first and test that? If I like that then how would I make it less glossy? 

 Link here to MC6G alternate glaze recipes using Custer or Minspar that Hesselberth and Roy put out. I don't know how old your Custer is or what the analysis for it is, maybe try a small 100 gram batch if you decide to use Custer before mixing up a bucketful. There is also a version of it using Minspar 200. On that link click on the "Mastering Cone 6 Glazes" tab then on "Glaze Reformulations".

Unfortunately it isn't a simple matter to take an existing glaze and add something to it to make it less gloss. Are you using it as a clear glaze or adding colourants and/or opacifiers to it?

[Bam2015]

Min, I am using it as a clear glaze.

 

 

[Min]

Okay, probably the simplest way to tone down the gloss level would be to do a volumetric line blend with a matte glaze. This just means you take equal volumes of your clear and a matte glaze then blend them together in different ratios. Both base glazes need to have exactly the same weight of dry materials and water. Info on how to do a volumetric line blend in this link if you need it. 

For the matte glaze recipe you could try the recipe below. It started out as a Tony Hansen recipe that I altered to use Ferro Frit 3134 as you already have that. Probably less than 20% of this matte recipe blended with your clear should take the gloss down enough and still be resistant to cutlery marking.

By doing it this way rather than start testing a bunch of new glazes you are making a glaze that will be predominately your existing glaze, plus you can fine tune how matte you would like it. Do note that the new glaze might have an effect on colourants as the matte is high in magnesium. If you try this please test it first before committing to a large bucket of glaze.

[Bam2015]

Thank you Min! I appreciate all of the work you did to respond to my question. I will check out the link that you sent. 

Betty

[Bill Kielb]

On 12/28/2022 at 8:13 AM, Bam2015 said:

Hello All & Happy Holidays!

I would like to make the following glaze a bit less glossy. It works great on my clay body, so I'd prefer to try to tweak this recipe rather than start with a new less glossy recipe. Any input would be appreciated.

EPK                        20.00

Ferro 3134        20.00

G-200                   20.00

Silica                     19.00

Wollastonite    15.00

The easiest way I can think of is slowly reduce the silica and see if you can satisfy your desired level of gloss. In effect you will be changing the Si:Al ratio (lowering it). In general a ratio of 7:1  ought to be glossy and as it decreases toward 6:1, 5:1 the finish should move towards matte.  Of course this can’t be done forever and may change the glaze fit but it’s likely the easiest thing to try.

Unfortunately the best you can do just removing all silica is 7:1 which in theory is still glossy. The epk, 3134 and wollastonite contribute significant silica already. Finally you have about 0.19 boron, if you are firing cone 6 you really only likely need 0.15, so maybe a quick test reducing the 3134 from 20% to 15% and the silica to zero or near zero as a quick try. That gets you into the 6:1 range and might be perfect for your look.

No guarantees, but pretty easy to try.

 

[Min]

6 hours ago, Bill Kielb said:

...and may change the glaze fit

Yup, and the durability. Glaze will still be high in sodium and fairly high in potassium, I'ld prefer to use an oxide(s) that contribute to matting.

Edited December 30, 2022 by Min

[Bill Kielb]

5 hours ago, Min said:

Yup, and the durability.

The sodium decreases very slightly, prox. 0.01, magnesium increases by .prox. 0.01 and calcium decreases by 0.01.  All a result of lowering the 3134. The flux ratio moves from prox  0.21:0.79 to 0.2:0.8, again a change of prox 0.01 all pretty immaterial and still in an expected durable range. so I would expect it’s still an easy way to try to work with the same recipe and reduce the gloss while not changing its durability. It may change the fit and certainly test durability but if it gets the desired look, an easy way to adjust the expected surface by following the expected gloss and also likely gets rid of the somewhat potential oversupply of boron as well. So could be a winner all around even saving on raw material. None of those numbers would be a relatively high or low change to me except the initial boron.

Probably should mention, your new 100% normalized recipe to record would be

epk 26.32

3134 19.74

G200 26.32

woll  19.74

talc. 7.89

otherwise just mix up a small batch as you have without silica and a 5% decrease in 3134 to try.  it just won’t add up to 100%. If it works, probably record the normalized above and keep that for reference / publication. As you can see it really has the effect of raising the relative portions of epk, g200 …… slightly by omitting others. Recipes that are mysteriously whole numbers such as 20,20,20 etc… often are many times the result of convenience for the initial trials. Folks optimizing recipes rarely land on a bunch of whole numbers so this Change may simply be an improvement on an old trial and error recipe.

Its hard to know by looking at the formula until you try it and of course test.

Edited December 30, 2022 by Bill Kielb

[Bam2015]

Thank you for chiming in Bill. I will give the new recipe a try & let you  know how it works out. 

Betty

[Min]

8 hours ago, Bill Kielb said:

The sodium decreases very slightly, prox. 0.01, magnesium increases by .prox. 0.01 and calcium decreases by 0.01.  All a result of lowering the 3134. The flux ratio moves from prox  0.21:0.79 to 0.2:0.8, again a change of prox 0.01 all pretty immaterial and still in an expected durable range. so I would expect it’s still an easy way to try to work with the same recipe and reduce the gloss while not changing its durability. It may change the fit and certainly...

Crazing could be an issue as COE goes from 6.8 to 7.5 (Same materials, nothing new added or taken away so COE is valid and applicable) Perhaps you could include a recipe for Betty using either Custer or Minspar 200 given G200 isn't available.

@Bam2015, when you test this I would suggest doing some delayed crazing tests on it. 

Edited December 30, 2022 by Min

[Bill Kielb]

1 hour ago, Min said:

Crazing could be an issue as COE goes from 6.8 to 7.5 (Same materials, nothing new added or taken away so COE is valid

Yes testing is good, definitely test. As far as calculated COE and whether it will craze, I have not found any real reliability or real world parallel to the fired COE. Some folks like the calculation some do not. Definitely test, I think that’s been suggested throughout. Even if the calculated COE did not change, always test to make sure it matches your clay.