Glazes Again

[Guest]

These are from my latest firing, a lot of surprises, some good some not so good.

 

1) This is the same batch of eggshell glaze as this post. I'm disappointed in the bottom with its ugly greenish gray color. I sprayed it thicker thinking it would more yellowish. The recipe has 9% tin oxide and I'm thinking of knocking that down to 4%. Do you think that might help?

 

 

  

2) This is the same Floating blue as in the same link above, I just added 0.5% more cobalt. I love this color

 

  

3) This is the same as the floating blue recipe expect when I was mixing it I accidentally used copper carbonate instead of cobalt carbonate. I was expecting some kind of green which shows up where it puddles and a light blueish blush here and there. I like this one too.

 

This one crazed but the one with cobalt didn't. Totally has me baffled since everything is the same except the carbonates.

 

These two are from the results from Marcia's suggestion. Both are from the same batch of base glaze and the one on the left has 0.5% Cobalt carbonate and the one on the right has 0.5% copper carbonate. The one on the right has crazed.

 

Any ideas why I'm getting crazing when I'm using copper carbonate?

 

 

[dhPotter]

Ron, beautiful Floating Blue!! Love the little swirls.

 

Hope someone can answer the Copper Carb/ Crazing question...

[oldlady]

ron, glazing is one of those things that are two steps forward, one step back.  except when it is the same thing in reverse.

 

i see crazing in the test tile marked 9 at the top left corner and also in the one above that, the jar marked 3.  you are on your way.

[glazenerd]

Any way to get an extreme close up of 8&9?

[Guest]

i see crazing in the test tile marked 9 at the top left corner and also in the one above that, the jar marked 3.  you are on your way.

Yes there is crazing in #3 but not in tile #9 I just double checked that with a loop. I do see what you are talking about because I see that in the image but not in the actual piece.

 

 

Any way to get an extreme close up of 8&9?

 

The best I can do until I get back to the studio, I left my camera there.

 

[glazenerd]

Ron:

Do you see the grainy texture on top of the cobalt, and some on the copper? Trying to see if that is unmelted silica. If you do not have a complete melt, can add to crazing issues. I still cannot see it clear enough: could just be the large particles in the stoneware.

 

Silica ratios certainly cause crazing. si/al ratio of this glaze?

[Guest]

The cobalt isn't perfectly smooth but it has a high sheen to it.

 

And yes, there is crazing on the cobalt, its difficult to see (but not for oldlady) but its there.

 

I'm using 325 mesh silica and there is only 10% in the recipe

 

Nepheline Syenite 30
Silica 10
Whiting 9.4
EP Kaolin 13.4
Talc 17.2
Gerstley Borate 20
Zircopax 5
Bentonite 2

 

I've been thinking of changing my base glaze to this just to see what happens.

 

mc6g low expansion    COE 6.17
Silica 25
Nepheline Syenite 20
Wollastonite 20
EP Kaolin 15
Ferro Frit 3124 20

[Min]

1 - no, you will loose that lovely rusty colour if you drop the tin that low.

 

I'm seeing crazing in the clear blue glaze also.

 

Ron, is this the classic Floating Blue recipe with 48% neptheline syenite? If it is the coe (coefficient of thermal expansion) is high because the nepsy is supplying a lot of sodium to the glaze, which is a high expansion flux. The higher the coe the greater the chance of crazing. The cobalt, rutile and iron will with a glaze calc program look like they are raising the coe even higher but in actuality those colourants have the effect of lowering crazing. 1/2% of cobalt carb has much more of an effect on crazing than 1/2% of copper carb hence more crazing in your green glaze. Floating Blue has been around for years, it's known to be very fickle with both thickness and firing schedules, it was called effing blue for a reason.

 

edit: missed it first time I read it but I don't think that's the low expansion glaze from mc6g.

screenshot below, your glaze in first column, what I have for the low coe mc6g in second. Have a look at 4th row down in the box on the lower left. What I have for their low expansion glaze with a coe of 6.17 is the recipe on the right.

[Joseph Fireborn]

If you want the eggshell to be more yellow add a small amount of yellow ochre. Say like .5% to start with. Of you could just do .5-2% to see the effects in your next firing. But the yellow ochre will darken that white into more of a pale yellow. 

 

That being said all the glazes look good.  Tile 8 and 9 both look crazed to me. 

 

I increased the exposure of your picture and unless something funky is going on on that tile there is obvious crazing you can see here:

 

[Guest]

1 - no, you will loose that lovely rusty colour if you drop the tin that low.

 

so the only way is to keep the glaze thin as in the first try?

 

 

1 - no, you will loose that lovely rusty colour if you drop the tin that low.

 

I'm seeing crazing in the clear blue glaze also.

 

Ron, is this the classic Floating Blue recipe with 48% neptheline syenite?

 

Only 30%,

 

 

I'm seeing crazing in the clear blue glaze also.

I Tile 8 and 9 both look crazed to me.

 

Yes you are both right it is crazed.

 

 

    edit: missed it first time I read it but I don't think that's the low expansion glaze from mc6g.

    screenshot below, your glaze in first column, what I have for the low coe mc6g in second. Have a look at 4th row down in the box on the lower left. What I have for their low expansion glaze with a coe of 6.17 is the recipe on the right.

 

Yes you are right, looks like it was Easy E Clear  COE 6.82 that I mislabeled Good catch Min, thanks. You know your stuff.

[Guest]

If you want the eggshell to be more yellow add a small amount of yellow ochre. Say like .5% to start with. Of you could just do .5-2% to see the effects in your next firing. But the yellow ochre will darken that white into more of a pale yellow.

 

I'll try that, thanks

[glazenerd]

Nepheline Syenite 30         Try this instead         Nep Sy          35.0 

Silica 10                                                               Silica             22.0

Whiting 9.4                                                          Whiting           9.5

EP Kaolin 13.4                                                    EPK               10.5

Talc 17.2                                                            Talc                 6.0

Gerstley Borate 20y                                           Gerst. Bor.      12.0

Zircopax 5                                                          Zirco                5.0                        COE 6.88

 

The alumina, calcium, and silica are at the upper end of limits.   Not sure why so much talc was thrown into a cone 6 recipe, do not need so much gerstley either. 

 

The original formula had silica levels well below limits.

 

Nerd

[Guest]

Will do, thanks

 

The one thing I've noticed is when I use Insight Desktop that the COE I get is higher than what others list here.

 

For example, Tom's is listed as 6.88 where as on my system the result is 7.4

 

mc6g should be 6.17 and on my system it reads 6.52.

 

Is this normal or do I have a setting wrong someplace

 

Tom's on the left and mc6g is on the right

 

[glazenerd]

Not familiar with Insight, I have never used it. There may be a toggle setting for COE?? I use Glazemaster 3.0, because it has formula limits written in the program; and a clay formulation module which I can program. I can also write my own formula limits, which I have done for porcelain, and almost done with stoneware. I check Ron Roy's website about every six months to update material files. Ron has many analyzed because of his clay formulation work.

[dhPotter]

Tom's recipe entered into my desktop Insight comes out with coe = 7.18 ???

 

These different coe from the same recipe using the same software caused from differences in materials database?

[Fred Sweet]

RonSa and dhPotter-

I think it may depend upon how current the analyses that you're using for each of the ingredients. Ron Roy enters a new analysis every time he orders his ingredients, and in the past kept the older ones dated in his files. You might want to check with Nerd about this.

Regards,

Fred

[neilestrick]

Copper affects the melt at cone 6, so it's not surprising that the copper glaze is different than the cobalt glaze.

[Min]

As well as updating ingredients profiles don't include the opacifiers and colouring oxides when quoting the COE, it's the base recipe that is referred to. dhpotter, if you exclude the zircopax in Tom's recipe what do you get?

 

Ron, I believe you made an error with the epk, it's 22, not 20 with the mc6g low coe. Glaze total is 100, not 98

[Guest]

Thanks Min

 

Here's a very large view of #3 glaze from the first post with three different clay bodies

 

All Standard Clay, from left to right: 760, 640, 112

 

 

As you may notice only the 640 has crazing the other two don't

[Joseph Fireborn]

I personally like the crazing in that glaze. I think it makes it more attractive. I am not sure if that is something you desire in your work or not. The forms you have been posting, these jars, I wouldn't worry about any crazing effecting sales on them, if anything it could increase them in my opinion. 

 

On another topic: Are you enjoying testing and stuff? Have you attempted to layer any of these glazes yet? One of the key things I have learned about cone 6 is not to try to push a single glaze really far, but to start layering them and watching magical things happen. I spent a lot of time trying to make one glaze do a lot, when I should have been spending time testing layering combinations.

 

Anyways, just a thought next time you run a test firing. Layer a bunch of these in different orders and see what happens. A lot of them will be ugly, but there will be a few that come out that are really neat. 

[Guest]

I think the crazing does work with that glaze on that clay body. Its interesting that it didn't craze on the other two, another lesson learned.

 

The only layering I've done so far is with commercial glazes, eventually I'll be layering the glazes I mix

 

An I enjoying the testing? It exciting, frustrating and confusing, coupled with my desire for learning I will be doing a lot more glaze tests. If it wasn't for this forum and the those that are willing to share their knowledge (and their patience with me) I'd still be trying to figure out what dry materials to buy and wouldn't be this far along.

 

Thank you everyone

[Min]

Will do, thanks

 

The one thing I've noticed is when I use Insight Desktop that the COE I get is higher than what others list here.

 

For example, Tom's is listed as 6.88 where as on my system the result is 7.4

 

mc6g should be 6.17 and on my system it reads 6.52.

 

Is this normal or do I have a setting wrong someplace

 

Tom's on the left and mc6g is on the right

 

Jul. 14, 2017 (750 x 452).jpg

 

I just updated all the ingredients in this recipe with my Insight, using the XML data from Insight, still get 6.17  Even with 2 less epk it doesn't account for the 6.52 you are getting. Think you have something screwy going on. I would update the MDT with your program for each material and see where the fault is. There is a video somewhere showing how to do this, only takes a few seconds to do each material. It's going to throw all your data off otherwise whenever the "faulty" analysis material is used. 

[dhPotter]

Min, Tom's recipe without the Zircopax now has coe = 7.14 in my desktop Insight.

[Min]

Min, Tom's recipe without the Zircopax now has coe = 7.14 in my desktop Insight.

 

That's what I get too. Tom's program is close enough to this to put the difference down to different material data. If you use the same program I think you get used to knowing what range works for your clay.

[glazenerd]

DH:

I have 5-6 nep Sy entries, all by dates. Like all things natural from the earth, variances across the country pending where it is mined. Yes, material updates can change Coe.

 

1. Sodium and potassium have very high Coe: as that % goes up in the recipe, so does the Coe.

2. Silica will lower Coe by marginal amounts.

3. Clays have roughly 1/2 the Coe of spars, larger additions lower Coe quickly.

4. Zircopax is the Coe killer, little drops Coe a lot.

 

Looking at the Coe of the raw materials you use the most, will give you a better sense of what raises and what lowers Coe.

 

Some very general / loose formulating notes.