Mixed My A First Batch Of Glaze

[Min]

Min - I do the SG test with glaze I know is mixed correctly... Yes? Then record that and use it to verify that "most" of my glazes are within the correct parameters before using?

 

To glaze, this is my current process:

 

Bisque to 04

Wax bottoms if needed (I like to do waxing first so then its easy to see if I missed a spot or have a spot I don't want)

Rinse quickly with water (either in a bucket or more often a quick swish under running faucet)

Let sit while I get my glaze ready (open containers, mix, etc)

Then either brush a couple thin coats on ( I brush east to west then north to south)

Or dip (I have found a count of 1001, 1002, 1003 works for most of my current glazes. There are some Mat glazes that this is even less since they tend to be chalkier in their application)

Or pour along with brushing or dipping (mugs, vases, pitchers, etc I use a plastic pitcher and pour the glaze inside then immediately pour it back out. Let this glaze dry which is usually pretty quick then either dip if I have an even rim or brush if it's variegated.

Set to dry

Use a use a piece of carpet glued to plywood to clean off the bottoms

FIRE!

 

YES I would like the brushing medium recipe you are so kindly offering. I really appreciate it.

 

T

 

Sure, sounds like a good place to start.

 

I don't rinse pots before glazing but if that works for you then go for it. 

 

Brushing Medium:

35 grams bentone (macaloid)

35 grams CMC

1 point 5 grams copper carb

1 gallon boiling water

 

Add the CMC gum to the boiling water (off heat) and let it sit overnight. Then take some of the CMC water and put it in a large yogurt container or something about that size and add the bentone to that and use a stick blender and blend for about 5 minutes. Add the bentone plus the copper carb to the CMC and mix the whole mess up. The bentone will want to just float around on top of the CMC gum water but will mix in with a stick blender.

(the copper acts as a preservative for the gum, it's just a tiny bit and doesn't effect the colour)

[jrgpots]

Another method to calculate the specific gravity is.

 

1. select any set volume. Today let's use 50ml. 

2. find the weight of 50  ml of water.  Let's say it weighs 50 gm.

3. find the weight of 50 ml of glaze.  Let's say it weighs  70 gm.

 

4. calculate:      weight of glaze    =    70   =  1.4   

                         weight of water         50

 

I often use a 60 ml syringe to draw up and measure 50 ml.

You can use a graduated cylinder or a volumetric flask to measure the volume accurately.

 

Jed

[Min]

Another method to calculate the specific gravity is.

 

1. select any set volume. Today let's use 50ml. 

2. find the weight of 50  ml of water.  Let's say it weighs 50 gm.

3. find the weight of 50 ml of glaze.  Let's say it weighs  70 gm.

 

4. calculate:      weight of glaze    =    70   =  1.4   This will always work as long as you measure equal volumes of material.

                         weight of water         50

 

I often use a 60 ml syringe to draw up and measure 50 ml.

You can use a graduated cylinder or a volumetric flask to measure the volume accurately.

 

Jed

 

um, since a 1 ml of water always weighs 1 gram I believe we are doing the same thing?   

[jrgpots]

 

Another method to calculate the specific gravity is.

 

1. select any set volume. Today let's use 50ml. 

2. find the weight of 50  ml of water.  Let's say it weighs 50 gm.

3. find the weight of 50 ml of glaze.  Let's say it weighs  70 gm.

 

4. calculate:      weight of glaze    =    70   =  1.4   This will always work as long as you measure equal volumes of material.

                         weight of water         50

 

I often use a 60 ml syringe to draw up and measure 50 ml.

You can use a graduated cylinder or a volumetric flask to measure the volume accurately.

 

Jed

 

um, since a 1 ml of water always weighs 1 gram I believe we are doing the same thing? 

 

 

 The point of my post was....you don't have to always start with  100ml.   

 

The formula for SG is :  weight glaze

                                      weight water        when measuring equal volumes.

 

Sorry if I came across poorly.

 

BYW   1 ml only equals 1 gm at 1 atmosphere and 3.93 degree C, the temp of water's maximum density.

 

jed

[oldlady]

ok,  you guys.  "a pint is a pound the world around" is the only thing i know.  how far off is that?

[PeterH]

ok,  you guys.  "a pint is a pound the world around" is the only thing i know.  how far off it that?

 

Not true I'm afraid. Almost true in the US, simply wrong in the UK.

 

From https://en.wikipedia.org/wiki/Pint

The imperial pint (≈ 568 ml) is used in the United Kingdom and Ireland and to a limited extent in Commonwealth nations. In the United States, two pints are used: a liquid pint (≈ 473 ml) and a less-common dry pint (≈ 551 ml). Each of these pints is one-eighth of its respective gallon but the gallons differ and the imperial pint is about 20% larger than the US liquid pint. This difference dates back to 1824, when the British Weights and Measures Act standardised various liquid measures throughout the British Empire, while the United States continued to use the earlier English measures. The imperial pint consists of 20 imperial fluid ounces and the US liquid pint is 16 US fluid ounces, making the imperial fluid ounce about 4% smaller than the US fluid ounce.

.

.

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One US fluid pint of water weighs about a pound (16 ounces), resulting in the popular saying, "The pint's a pound, the world around." However, a US pint of water weighs 1.04375 pounds and the statement does not hold the world around because the imperial (UK) pint, which was also the standard measure in Australia, India, Malaya, New Zealand, South Africa etc., weighs 1.25 pounds. A different saying for the imperial pint is "A pint of pure water weighs a pound and a quarter."

[oldlady]

OK!  here is a math problem for you guys who know how to use a calculator.  if i make 1000 grams of dry glaze, how much water should i add to it?  

 

my faulty math has told me that about 3/4 of the weight of the finished glaze is water so i usually use my pint measuring cup.  if a pound is 454 grams, 1000 grams is just over 2 pounds so i use 1 pint plus 2/3 cup water.  and usually have too much so i remove some the next day and save it for adding as i use the glaze.

 

is there a simple way to figure it out?

[Min]

OK!  here is a math problem for you guys who know how to use a calculator.  if i make 1000 grams of dry glaze, how much water should i add to it?  

 

my faulty math has told me that about 3/4 of the weight of the finished glaze is water so i usually use my pint measuring cup.  if a pound is 454 grams, 1000 grams is just over 2 pounds so i use 1 pint plus 2/3 cup water.  and usually have too much so i remove some the next day and save it for adding as i use the glaze.

 

is there a simple way to figure it out?

 

OldLady, you are making it harder than it needs to be.  If you want 3/4 of 1000 grams that would be 750 grams of water. (if you don't want to weigh the water that would be 750 ml - want me send you a metric measuring cup?) 

 

edit:

If the weight of the finished glaze is 1750 then 3/4 of that weight would be 1312.5 of water which seems awfully high. I'm guessing that 3/4 of the dry glaze materials weight would be closer to what you are aiming for (plus more water to get it just right of necessary).

[Celia UK]

It would certainly help if you used metric measurements over there! There is actually a formula related to this question but I'm away on holiday and can't lay my hands on it until I return. I'll try to remember to dig it out & post it!

 

Another tricky one is the 'cup' as a measurement. In the UK a cup can be any amount at all - whatever size your cup is! We don't have a standard cup measurement, nor a 'stick' of butter that I've seen in US recipes!

[jrgpots]

 if i make 1000 grams of dry glaze, how much water should i add to it?  

 

 

is there a simple way to figure it out?

 Using the formula:  weight of dry glaze + weight of water

                                      weight of water                                     =  SG

 

Let's see what we can come up with.

 

                                 1000 gm + x 

                                         x                        = SG

 

 

therefore                 SG(x) = 1000 + x

 

 

Let's say you want SG = 1.45

 

then                        1.45(x)  = 1000 +1.5

 

                                       x   =   1001.5

                                                    1.5

 

                                       x   =   667.6 ml

 

                                                 667.6 ml = 22.6 fl oz.

 

 

You were really close. that is 1 pint and 6.6 fl oz (just over 3/4 US cup).

If you are skimming some off the next morning, your specific gravity would increase to 1.55 to 1.6.

 

 

Jed

[Pieter Mostert]

I think the formula Celia referred to is Brongniart's formula, which effectively says that the specific gravity of a glaze is the weight of the dry ingredients plus the weight of the water (in grams), divided by the volume of the dry ingredients plus the volume of water (in ml). Really, it's just saying that specific gravity is the weight divided by the volume.

For most glazes, the volume of the dry ingredients is equal to the weight of the dry ingredients divided by about 2.5, so if D is the weight of your dry ingredients and W is the weight of water (which equals the volume of water, in our units), then

SG = (D + W) / (D/2.5 + W)

Using D = 1000 and W = 631 (the volume of 1 pint + 2/3 cups in ml, if I've converted it correctly), you get SG = 1.58. It's a little on the high side, so I'm a bit surprised you need to decant water, but perhaps the value of 2.5 isn't quite right for the glaze you're using.

If you want to find out how much water to add to a batch of dry ingredients to achieve a certain specific gravity, you can solve the formula above for W. You should find that

W = D * (1 - SG/2.5) / (SG - 1)

So if you wanted a SG of 1.5, for example, you'd need to add 800ml of water to your 1000g batch of dry ingredients.

 

EDIT: I've fudged over the fact that the volume of the dry ingredients isn't the actual volume you'd measure, it's the volume you'd get if you could remove all the air between the particles. But this isn't something you need to worry about.

[oldlady]

celia, thank you!  on holiday where?  wherever it is, have a great time, build memories for those other days ahead.  BTW  a cup equals 8 ounces.  a stick of butter is a quarter of a pound so 4 ounces.  you would find it hard to make oatmeal cookies from the recipe inside the oatmeal container.

 

jrg, thanks, i will ask a friend who PASSED algebra to interpret the figures and symbols.  

 

peter, so, by accident i am almost right with my seatofthepants quasimath.

[dhPotter]

OldLady this is really simple.

 

Use 3 ounces of water to 100 grams of dry weight.

 

1000 grams divide by 100 grams = 10. 10 times 3 = 30 ounces.

 

1000 / 100 = 10 * 3 = 30. This is a starting point, may need to add more.

[jrgpots]

Thanks Peiter.

 

Jed

[Pugaboo]

You guys are making my head hurt... And have me considering a dash back towards the commercial glaze side of life, they at least don't ask me to do algebra. I am blonde for a reason! Seriously though I need to learn this even if it IS math (blek gag).

 

Dhpotter - your formula I might maybe sort of be able to remember and use. Thank you! I will print it out super big and paste it to the wall over my glaze table. 3 ounces per 100 grams of dry glaze.

 

I do have a question though.

If I measure 1000 grams of base glaze materials and then add in the colorant the dry glaze mixture it now weighs more than 1000 grams so do I measure THIS mixture or do go by just the base grams? I think my head just imploded as my brain ran for the door.

 

T

[Magnolia Mud Research]

If I understood all the back and forth (is that make it froth?  )

you use the total solids as the basis for estimating the amount of water to use.

 

at least that is how I do it, and it works for me.

 

If I don't have a previous batch to use as a starting point I start with 60 grams (ml) of water for every 100 grams of total solids.  this makes the water to solids ratio = 60/100 or 0.6. 

 

LT

[Callie Beller Diesel]

Everyone needs to stop thinking about it so hard. The ideal specific gravity of any given glaze is dependant on your personal preference. It's something you record so you can repeat your results, or troubleshoot.

And unless you like headaches, stick to one system of measurements: Imperial or Metric. Combining them, or constant conversions between the two are a good way to mess with an otherwise good day in the studio.

 

If you weigh out 100g of glaze, just add about 50 or 60 ml of water (the measurement is close enough to the same number of grams at room temperature) and its usually enough to get it through the sieve. The glaze will likely be a bit thick for practical application, but you can then add water after that to make the consistency you want.

[Babs]

Going way back if you are first brushing the scalloped edge then almost immediately dipping, this may be the reason for the thinning of glaze on the rim

[Celia UK]

Everyone needs to stop thinking about it so hard. The ideal specific gravity of any given glaze is dependant on your personal preference. It's something you record so you can repeat your results, or troubleshoot.

And unless you like headaches, stick to one system of measurements: Imperial or Metric. Combining them, or constant conversions between the two are a good way to mess with an otherwise good day in the studio.

If you weigh out 100g of glaze, just add about 50 or 60 ml of water (the measurement is close enough to the same number of grams at room temperature) and its usually enough to get it through the sieve. The glaze will likely be a bit thick for practical application, but you can then add water after that to make the consistency you want.

I must agree Diesel - on all counts above.

 

Back from holiday (cruise on the Rhine, Old Lady - BTW thanks for info on cups and sticks!!)) - I looked up my notes to find the formula and Pieter was right thinking the formula I remembered was Brogniart's. When I first came across It a few months ago, I saw that it came out pretty close to the guesstimate starting point I'd been doing anyway and wondered why there was such a complicated way of getting there.

[Pieter Mostert]

Diesel Clay's right, of course. You don't need Brongniart's formula to work out how much water to add, and in fact this isn't why Brongniart came up with his formula. The usual way in which the formula is presented expresses the weight of the dry ingredients in terms of the weight and specific gravity of the glaze. This is useful if you have a batch of glaze that you've been using for a while, but want to modify the composition.

[Callie Beller Diesel]

Don't get me wrong, I enjoy a good derailment of a thread via technical minutiae as much as the rest of us

But I think threads like this one are the reason people new to glaze chemistry are needlessly afraid of some of the calculations.

Brongiarts formula is also handy if you've messed up an ingredient when adding to an existing batch of glaze, but it's not part of the beginner class.

[jrgpots]

Pugaboo, I 'm sorry for As Diesel said, "Derailing" your thread with technical minutiae. My efforts to help did just the opposite. I am not formally trained in Ceramics/ pottery and my exposure to the use of specific gravity is very different from the standpoint of pottery.  I had never heard of Braongniart's formula or knew that the specific gravity of dry glaze materials is somewhere around 2.5 - 2.65 until after I posted on the thread.  I forget just how much I don't know in this field and how much knoledge is found in this area and on the forum.  My major was microbiology with a minor in chem/physics in undergraduate school.  I therefore enjoy math.. sorry for my rant.

 

Old Lady, Pieter, Deisel, Min, Celia, and others...I think I'm gonna watch a whole lot more and chime in a whole lot less...and only to ask questions.

 

Jed

[oldlady]

jed, i am making a note that you are the one to call when i get confused by percentages.  could not believe what i almost did yesterday, took 100 grams of mixed dry glaze ingredients and wanted to use 1% copper.   measured out the 1% and then  realized i would only need a small amount so measured out 10 grams of the glaze, stirred it up in water, brushed it on, added another 1% copper and then noticed that the color was very deep.   duh............................................

[Babs]

Pugaboo, I 'm sorry for As Diesel said, "Derailing" your thread with technical minutiae. My efforts to help did just the opposite. I am not formally trained in Ceramics/ pottery and my exposure to the use of specific gravity is very different from the standpoint of pottery.  I had never heard of Braongniart's formula or knew that the specific gravity of dry glaze materials is somewhere around 2.5 - 2.65 until after I posted on the thread.  I forget just how much I don't know in this field and how much knoledge is found in this area and on the forum.  My major was microbiology with a minor in chem/physics in undergraduate school.  I therefore enjoy math.. sorry for my rant.

 

Old Lady, Pieter, Deisel, Min, Celia, and others...I think I'm gonna watch a whole lot more and chime in a whole lot less...and only to ask questions.

 

Jed

Please don't Jed, I think the fact that a lot of us come from different 'angles" is a true strength in solving many of the probs. posed.

Please keep giving your thoughts.

It's all the htings we thought we'd never need that we do need in this area.

People can scan and ignore what they find irrelevant at the moment

[Pugaboo]

Jed, any help is good I just sometimes doesn't understand it! So please chime in as often as you want to! I will eventually understand even this aspect of pottery. 3 years ago I didn't even know what RIO was and was clueless when it came to anything to do with a kiln and now I know all kinds of things I never even knew existed and I wouldn't if it weren't for all the super helpful people here sharing their knowledge.

 

I have always had an issue with numbers, I'm smart enough to teach myself algebra (home schooled with little help from others scored high enough in final test not to need remedial classes to get into college courses) but realized long ago I think in shapes and images rather than numbers and formulas, I guess something along the lines of thinking visually. Tell me you want a mural to go a certain place and leave me to it and I will have a scale and detailed blueprint of the area involved and how best to make the image look right in perspective from all angles. Just don't tell me that I need to divide this ratio by that number multiplied by this equation. My brain just doesn't work that way.

 

EVERYONE never feel that your sharing of knowledge is not appreciated. It is most humbly so.

 

T