Question on mixing colorant batches

[kraythe]

I have found a clear glaze that doesn’t craze on my cone 5 Porcelain in mid range and I would like to  experiment with some colorants. I don’t especially want to mix every batch separate if I can avoid it so I was wondering if the following strategy would be valid. 

First mix up 5 gallons of the clear. Get it to specific gravity of 1.40 which is great for dipping this glaze. Then measure off smaller batches of 140g of glaze which should be 100g of base then add the colorant amounts and then mix well and apply glaze. This would leave me with a much more manageable and less annoying job than mixing every 100g batch separately 

So is this viable?

[Mark C.]

I always do glaze tests starting with dry weights

lets say you want to add cobalt in 5% additions

mix up 100 grams with the starting 5% of cobalt then dip a tile then add another 5% of cobalt -that will equal 10% dip a tile and so forth.That way you are adding the right amount in dry weight to your original batch

You can do the wet thing but I feel there is more room for error in small batches to begin with and wet just adds more variables.

Thats my 2 cents

[neilestrick]

I agree with Mark. Working with wet batches adds another variable that can really mess things up, especially with colorants, which may be using as little as 1/4 of 1%. You'll have greater accuracy working with dry weights. But you can mix up a few thousand grams of the base and just use that 100g at a time. Just be sure to dry mix the big batch really well.

[Tyler Miller]

It should work, as long as your math is right.  There are a few reasons why working wet can be desirable, even.  Dry mixing glazes being a messy job is the main one.  In certain parts of the world, working with wet ingredients is the norm and glaze recipes are measured volumetrically.  It’s just what you’re used to and comfortable with.

If I’m not mistaken a member mixes line blends/curry grids at least semi-wet?

As long as your math is right, your base glaze well mixed (so it’s the same SG all the way through) and your scale accurate, it should work fine.  

[Joseph Fireborn]

Edited. Need to check some calculations first.

[JohnnyK]

14 hours ago, Mark C. said:

I always do glaze tests starting with dry weights

lets say you want to add cobalt in 5% additions

mix up 100 grams with the starting 5% of cobalt then dip a tile then add another 5% of cobalt -that will equal 10% dip a tile and so forth.That way you are adding the right amount in dry weight to your original batch

You can do the wet thing but I feel there is more room for error in small batches to begin with and wet just adds more variables.

Thats my 2 cents

I am guessing that you are mixing the first batch dry, adding water to bring the SG to dipping level, dipping the tile and then adding another 5% cobalt to the wet mix to bring it up to 10%. If so, I think that dipping the tile will reduce the original volume and adding the additional 5% would bring the concentration to slightly more than 10%. Not so much a problem with cobalt, but when you get into adding fractions of a %, it could be detrimental to the outcome ...

I think that using the wet method, but making a smaller volume, like maybe a gallon instead of 5 gallons would make it easier to mix and keep the glaze components in suspension for mixing the smaller batches of colored glaze...

[kraythe]

I could mix it dry and dip out of that but you have to have a very very good mix and using power drills and so on to mix drys is bound to generate a ton of hazardous dust so that’s why I was thinking wet mix and right Specific Gravity (SG)  then add colorants. Also with doing it dry I have to laboriously set the SG per batch of colorant and that is mind numbingly tedious. If I set the SG first then it’s done for all the batches.

[Min]

for reference: http://www.potteryatoldtoolijooaschool.com/brongniarts_formula_made_easy.pdf

[Mark C.]

2 hours ago, JohnnyK said:

I am guessing that you are mixing the first batch dry, adding water to bring the SG to dipping level, dipping the tile and then adding another 5% cobalt to the wet mix to bring it up to 10%. If so, I think that dipping the tile will reduce the original volume and adding the additional 5% would bring the concentration to slightly more than 10%. Not so much a problem with cobalt, but when you get into adding fractions of a %, it could be detrimental to the outcome ...

I think that using the wet method, but making a smaller volume, like maybe a gallon instead of 5 gallons would make it easier to mix and keep the glaze components in suspension for mixing the smaller batches of colored glaze...

Dick you are right about the glaze missing on the tile but  its a small amount .I was speaking in general-myself I always use 500 gram tests as 100 gram amount  the error is huge and easy to screw up.

I like to weight it all out mix up the 1st one wet and dip then add dip then add. They're are just tests and once one appeals to you you test it further by itself made as a single whole unit .

Measuring liquid volumes even in a centimeter tube is always to a slight degree a judgement call as to the line-compared to a gram scale of weight unit-that really is my point here.

Thats why I dry weigh then add to for tests. Both will work but I feel the dry one reduces some errors.

[Magnolia Mud Research]

Yes, it is viable! 

I use an equivalent strategy frequently when I am working on tweaking glazes.  I also keep track of the water/solids weight ratios for all glazes.  This helps making derivative glazes quick and simple. 

There is a built-in assumption that you must keep in mind:
The big batch has a uniform water to solids weight ratio throughout the batch.  This can be achieved by thorough mixing. 

Your proposal is the same principle as the Ian Currie technique of glaze mixing.  Currie calls it volume mixing.

LT

[kraythe]

4 hours ago, Mark C. said:

Dick you are right about the glaze missing on the tile but  its a small amount .I was speaking in general-myself I always use 500 gram tests as 100 gram amount  the error is huge and easy to screw up.

I like to weight it all out mix up the 1st one wet and dip then add dip then add. They're are just tests and once one appeals to you you test it further by itself made as a single whole unit .

Measuring liquid volumes even in a centimeter tube is always to a slight degree a judgement call as to the line-compared to a gram scale of weight unit-that really is my point here.

Thats why I dry weigh then add to for tests. Both will work but I feel the dry one reduces some errors.

I will point out that you don’t need to look at the line if you know the specific gravity. Assuming the glaze is well mixed and the SG is 1.4, then 140g of wet glaze by weight will give you 100g dry raw.

[kraythe]

36 minutes ago, Magnolia Mud Research said:

Yes, it is viable! 

I use an equivalent strategy frequently when I am working on tweaking glazes.  I also keep track of the water/solids weight ratios for all glazes.  This helps making derivative glazes quick and simple. 

There is a built-in assumption that you must keep in mind:
The big batch has a uniform water to solids weight ratio throughout the batch.  This can be achieved by thorough mixing. 

Your proposal is the same principle as the Ian Currie technique of glaze mixing.  Currie calls it volume mixing.

LT

Thanks a bunch. Yeah I did assume well mixed glaze.

[tinbucket]

This video will help you. The method he suggests is similar to what Mark C said. Mix 200g of glaze, add a bit of your colorant, brush a stroke on the tile, add a little more colorant, brush a stroke on the tile, and so on. One thing that may be helpful is to look at other recipes to see how much of each colorant is added. For example, 5% iron oxide might not do much to the color but 5% cobalt carb would give you a metallic runny blue (<<<almost positive).  Another thing that may be helpful is to add an opacifier such as tin oxide or zircopax to some of your tests to see how it changes the color. There's also the possibility of colorant combinations, many of which are documented in glaze recipes. There is also a John Britt video where he demonstrates the method you originally suggested but I think the above method is less wasteful and more efficient. 

[Joseph Fireborn]

Okay. I had previously posted this but I took it down because I thought I had made a mistake on one of my cell calculations, but I have checked it and everything is fine.

I do colorant test a lot, or I used to. I used to weigh out 5 batches and then weigh 5 additions. It was cumbersome and a waste of time. I also don't like mixing dry as its absurdly dusty unless you have a ball mill(without the balls) to put the bucket on, and then again it's not simple for small batches. Eventually, I decided to go about making a quick sheet to get the math right fast.

I have created a page to do simple testing of glaze additions that are dry into a batch of wet glaze here: 

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LINK REMOVED UNTIL I FIX ERROR DONT WANT SOMEONE USING IT UNTIL I FIX MY MATH THIS EVENING WHEN I GET HOME 

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The fourth sheet is the sheet that you are interested in. It is called Glaze Measuring.

It has 4 cells you can enter information into that have a green background:

1. total cups: How many test cups you want to create

2. ml per cup: how many ml of the base glaze(wet) you want to put in each cup

3. dry weight: total g ingredient of your master batch(the big batch you mix for each small cup)

4. specific gravity: dry to water ratio

The green checkmark(total approximate grams used) is there to make sure that your dry ingredients are more than your grams used, it seems obvious, but...

--

After you put in the required data you will get the amount to add to each cup that you want to test below in the table called Dry Addition Method.

Say you want to do random amounts of certain stains with your clear base for your porcelain base you would just quickly enter the information that you want to test, and get the outputs for the dry in the table.

Mix up your test batch of base glaze enough to fill the 10 cups with the same amount per cup to the specific gravity(eq.vol) that you desire. Then weigh the increments quickly with your accurate scale and go about your business.

The best part about this is you can quickly mix all sorts of ideas. Say you want to test 5% RIO and 1% tin, or 2% cobalt and 1% mason 6600. All of these become really easy to do.

Also pro tip for mixing small test cups after adding in the small dry ingredients. Get a milk frother, it works so well. https://www.youtube.com/watch?v=GzxTaCfGji8

Anyways. Hope this helps. The method you are wanting to do works perfectly fine. I will say that you should test larger batches before going to a production batch just to be certain you did everything right. Go from 100ml test to 1500ml to production or something just to be certain you haven't made any mistakes.

[Pieter Mostert]

On 03/03/2018 at 10:44 PM, kraythe said:

 Then measure off smaller batches of 140g of glaze which should be 100g of base

If your s.g. is 1.4, then assuming the relative density of the materials in your glaze is 2.6 (see the pdf Min linked to), you'll only have 65g of dry materials in 140g of glaze.

You can work this out as follows: Let D be the weight of the dry materials, and W be the weight of water (in grams). Then since the relative density of the dry materials is 2.6, the volume of the dry materials in the glaze is D/2.6, and since the relative density of water is 1, the volume of water is W/1 = W (in mililitres).  Therefore the weight of the glaze is D + W, and the volume of the glaze is D/2.6 + W, so its specific gravity is

sg = (D + W) / (D/2.6 + W)

With a bit of algebra, you can express D in terms of sg and W, or W in terms of sg and D. However, in practice, you usually only know the specific gravity and the total weight, T, of the glaze. In this case,  since T = D + W, you have W = T - D, which when you plug into the formula above, gives

sg = T / (D/2.6 + T - D)

      = T / (T + (1/2.6 - 1)*D)

Now you can solve for D in terms of T and sg:

D = T * (sg - 1)  / sg / (1 - 1/2.6 )

   = (13 / 8) * T * (sg - 1) / sg

Plug in T = 140 and sg = 1.4, and you'll get D = 65.

[Joseph Fireborn]

Pieter is my math wrong then? Cause I am not getting those figures on my Glaze Calculations page, but I thought I had worked the math out correct on my previous calculations? Maybe because I didn't use SG on those other calculations because I was using equalizing volume to do my glaze test. I don't really use SG much when I am testing glazes only after I have got the glaze where I want.

Edit: Looking back at my currie numbers, when I use 100ml per cup I get 64g of dry. Something isn't right somewhere. I need to check my calculations. I knew I had edited it a while back, but I think I must have left in my error. Which is why I took down the post on Saturday.

[High Bridge Pottery]

64 seems pretty close to 65, I tried to understand the spreadsheet but I am to tired.

[Joseph Fireborn]

23 minutes ago, High Bridge Pottery said:

64 seems pretty close to 65, I tried to understand the spreadsheet but I am to tired.

It is, but on my new sheet, the one I created and linked the math is wrong. I was changing the layout the other day and adding some things for measuring wet additions and I screwed up my calculations on the 4th sheet. I know the other ones are right, but the 4th one is definitely wrong. I will fix it later.

[Pieter Mostert]

6 hours ago, Joseph F said:

4. specific gravity: dry to water ratio

Maybe this is where the mistake is? Specific gravity is the ratio of the weight of the glaze to the weight of an equal volume of water.

[Joseph Fireborn]

I know what I did wrong now. I just need to fix it and I will update the link for the OP. Thanks for spotting that, would have hated to be responsible for a bunch of failed test.

[Joseph Fireborn]

Okay.

I think this is right now. I plugged in your formula Pieter and it checks out with the math on my currie page for additions. Glaze Measuring ( 4th page ) 

https://docs.google.com/spreadsheets/d/1faETrVYo0Lin_2LU7GYK2BgvOuVLf3cCpefjQzRC5ns/edit?usp=sharing 

^^ the above link is still not correct for general use.

[Marcia Selsor]

I used a similar system for color development. I learned it in the 60s and used it when I ws teaching. I posted it here several times over the years but not lately. I mix 250 gr. of the base. Add water to a glaze consistency. Pour equal amounts into 5 cups ( 50 grams of dry mix in the batch)  labeled A,B,C,D,E.. . have a 6th cup for the mixing. Have 15 tiles prepared, bisued and numbers 1-15. Add a good variety  of colorants. Example: A=base add a colorant to the base if you like.  B-3% iron Ox. , C=2% copper carbonate, D=1% cobalt carbonate, E. 5%rutile  The weights are 1/2 of the % amount since it is a 50 gram batch in each cup.. Ex.  1.5 grams for 3%  for the iron.  Mix in and sieve.

1st row is straight from the cups   A, B,C,D,E 

2nd row    Mix a teaspoon of A with each of the others    A+B, A+c, A+D, A+ E   this reduces the colorants by half 

3 row   Mix B+C, B+ D, B+ E  this reduces the colorants by half 

4th row  C+ D, C+ E  this reduces the colorants by half 

5th row  D+ E   this reduces the colorants by half 

this gives 15 color variations relatively quickly. and only one dry mix.

Marcia

 

[neilestrick]

On 3/3/2018 at 9:59 PM, Tyler Miller said:

If I’m not mistaken a member mixes line blends/curry grids at least semi-wet?

Correct. But in Curry blends, you're blending, not adding materials to a base, and you're doing the blends by volume. You weigh out the 4 corners of the blend to the same amount, then mix the same amount of water into each one, regardless of how thick or thin the mix is, so you have the same volume batch of each corner. Then you do the blends by volume. A syringe is the easiest way to do it.

[Pieter Mostert]

4 hours ago, Joseph F said:

Okay.

I think this is right now. I plugged in your formula Pieter and it checks out with the math on my currie page for additions. Glaze Measuring ( 4th page ) 

https://docs.google.com/spreadsheets/d/1faETrVYo0Lin_2LU7GYK2BgvOuVLf3cCpefjQzRC5ns/edit?usp=sharing 

 

Based on the formula you use for F4 in the Glaze Measuring spreadsheet, cell B4 should be the weight of glaze per cup.

[Tyler Miller]

@neilestrick

I’m sorry,  my wording wasn’t so precise.  I meant more that working volumetrically isn’t an issue, can be precise, and that it isn’t a big ask to do what the OP intended because the knowledge base is there.  And I do believe the curry grid gents who possess that knowledge have obliged in figuring out what needs to be done.