Dave's Blue

[Chantay Poulsen]

I got the following recipe from a studio where I was taking class.  I can't figure out how to recalculate the amounts.  I want to be able to mix up about 100 grams for a test sample, then about 2000 grams for a bucketful.  I entered the amounts into insight, but don't know enough to manipulate it.  Any help would be appreciated.

-chantay

borate, Gerstley      2500

EPK                           875

Flint                          1750

Cobalt Oxide                50

Copper Carb               100

Rutile                           150

[Nadine Mercader]

If you add the contents for the glaze without colorants = 5125 grams.  The colorants are the cobalt, copper, and rutile.  Figure out what percentage of that total each is

A.Gerstley Borate  2500= 48.78% of total 5125 grams

B.EPK 875 = 17.07%  of total 5125 grams

C.Flint = 34.15% 

A+B+C = 100%

+ Colorants

Cobalt Oxide = 2% (rounded up from.019512)

Copper Carbonate =  2% (rounded up from.019512)

Rutile =  3% (rounded up from.02926)

So for a 100 gram batch (I think that is too small a quantity for a good test,  I would use 250 grams.

100 grams batch 

A.Gerstley Borate = 48.78 grams

B.EPK = 17.07  grams

C.Flint = 34.15

Colorants  

Cobalt Oxide = 2% = 2 grams

Copper Carbonate =  2% = 2 grams

Rutile =  3% = 3 grams

The math is not tough on this one good luck.

[Chantay Poulsen]

Thanks Nadine,  I have done this before but for some reason couldn't get it to work out??  Maybe I multiplied when I should of divided.  I use to have notes on how to do this but lost them.  I will save your post for in the future.  Thanks again.  And  I will do the 250 grams and see how much it makes.

-chanta

[Nadine Mercader]

Chanta,

The key to it is to first divide the list into the glaze components + the colorants.  Then add up only the glaze components, in this case GB, EPK, FLINT = 5125.

Then divide 2500 by 5125 = 0.487804 (48.78%).  Do that calculation for each of the glaze components and then add the 3 figures together and they should equal 100%

Then repeat the process for the colorants. 

Once you have the percentages it is easy to determine how much you need of each in your test batch.  One really important thing that I keep in mind when deciding to make a test batch is that 454 grams = 1 pound.  

When I test glazes I like to do tile tests of 1 coat, 2 coats, 3 coats or sprayed light,  whatever plus I always like to test on a bowl because I can see how it moves in the curve.

I would love to see what your glaze comes out like.

Nadine

[Chantay Poulsen]

Thanks, I had been taught this at a glaze class but for got.  I have my test batch mixed up and bisque ready to go.  After I measured out each ingrediant and dry mixed in a cup I put it back on the scale to see if it added up to 250.  It didn't. I think my $15 scale was off.  So I ordered a new one.  Hopefully it won't be off too much.  When the new scale comes in I will redo test batch.  I have a copy of all the glazes that the studio where I took classes.  I hope to use about 8 of them.  I will post my results.  I also plan to put them on Insight.

-chantay

[Nadine Mercader]

Fortunately,  I bought an accurate digital scale with a tare feature many years ago since I am too poor to buy anything these days.  I can't wait to see your results.

Nadine

[Chantay Poulsen]

Here is the corner of a platter in Stadards Red rock, cone 6, I glazed in the Dave's Blue. It is clear with a touch of dark blue where thin to the lighter blue where thick. 

[Norm Stuart]

Your Dave's Blue shares the same Rutile process for creating the blue areas as do "Gartside 28 Base - Peacock Version" and the long popular "Floating Blue - Ron Roy".  Both of these recipes are available in our Insight-Live glaze database.

This 2008 posting on Clayart explains the chemical mechanism behind this.  It's is not easy reading, but the explanation is quite complete.

http://www.potters.org/subject107948.htm

"Gartside 28 Peacock" using Ferro Frit in place of Gerstely Borate  (this recipe can be found in our Insight-Live Database)  It contains Rutile and Copper Carbonate, without the Cobalt Oxide.

Your Dave's Blue example.

Honey is another similar glaze, but without the Cobalt Oxide and Copper Carbonate.

[Nadine Mercader]

Norm, 

I love your Gartside 28 Peacock,  the thin green is very nice and blue where it pools is definitely reminiscent of floating blue.  Do you have a finished piece made from this glaze?  

[Chantay Poulsen]

Thanks for the info Norm. Will try and read tonight. That Peacock looks good. The Gartside base is on my list to try. I just switched to a red clay and the clear I have now looks like cat puke.