An experiment in Fritware Zero3

[Joseph Fireborn]

Nice research Joel.

[High Bridge Pottery]

Thank you  

[PeterH]

A few thoughts on your crystals

- As you cannot dissolve them in hot water this might indicate that they aren't boron-based.

- If you have dilute hydrochloric acid it will dissolve most calcium salts, including the silicate
... see A in http://www.pharmacopeia.cn/v29240/usp29nf24s0_m12120.html

If you find a way of reproducibly creating the crystals it might be interesting to try:

- Using a different deflocculant (Darvan?), which will probably change the pH of the slip which might change things.

- Seeing if a small addition of sugar to the fresh slip influences the growth of the crystals [*]

[*] Adding sugar would probably be very bad for the moulds, but just might form an interesting experiment. I mention it because sugar has a significant effect on the settling time of cement, apparently by its surface action on things like Wollastonite.
 

 

Edited February 12, 2023 by PeterH

[High Bridge Pottery]

Thank you for the ideas on some test Peter, I will source some HCl soon and report back the results. Will have to look into the sugar and see what that is meant to be doing.

[Callie Beller Diesel]

@High Bridge Pottery, I don’t know about the UK, but HCl is used here to etch concrete for painting. I can get it at Canadian Tire, so maybe check DIY friendly stores?

[Bill Kielb]

On 2/12/2023 at 8:45 AM, High Bridge Pottery said:

I will source some HCl

Also, Pool supplies (ph adjustment) also known as muriatic acid, or dilute hcl.

[High Bridge Pottery]

46 minutes ago, Callie Beller Diesel said:

I don’t know about the UK, but HCl is used here to etch concrete for painting. I can get it at Canadian Tire, so maybe check DIY friendly stores?

Yes looks like I can source it there, thanks for the tip Callie. Not so sure about pool supplies in the UK Bill  I am sure there's commercial suppliers but not many people have their own.

[PeterH]

2 hours ago, High Bridge Pottery said:

Yes looks like I can source it there, thanks for the tip Callie. Not so sure about pool supplies in the UK Bill  I am sure there's commercial suppliers but not many people have their own.

It might be worth trying excess hot vinegar first.
Mechanism and kinetics of wollastonite fibre dissolution in the aqueous solution of acetic acid
https://www.sciencedirect.com/science/article/abs/pii/S0032591010005267?via%3Dihub
The dissolution of fibrous wollastonite (CaSiO₃) in the aqueous solution of acetic acid (3 mol dm^− 3) was investigated in the temperature interval from 25 to 50 °C using mixed batch-type reactor.

I'm a bit uncertain, but I think that 3 mol dm^− 3  is about 18% vinegar. The pickling vinegar I use for descaling my kettle is 6%, so it would be weaker than that used in the paper, but might still be strong enough to dissolve your crystals (if they are derived from Wollastonite).  Perhaps worth trying before you buy the HCl.

PS You might be wise to check my workings.
Molar mass of acetic acid ~60g  https://en.wikipedia.org/wiki/Acetic_acid
1dm = 10cm. 1 dm ³   = 1000ml = 1 litre
So 3 mol dm^− 3  = 3*60g/l = 180g/1000g = 0.18 = 18%

 

[High Bridge Pottery]

Thanks Peter, will either of these dissolve the silica or will that still remain with both the hydrochloric and acetic? 

One reason I wanted the HCL was because I could also try doing a flame test and see if that gave any clues as to what I have, although lithium and calcium seem close in colour. I am looking to do some lime mortaring of my house this year so it might be worth buying the HCL concrete etcher or brick/mortar cleaner anyway as I am not very good at keeping the bricks clean.

Edited February 14, 2023 by High Bridge Pottery

[Callie Beller Diesel]

@PeterHfrom that same wiki, 

“A 1.0 M solution (about the concentration of domestic vinegar) …”

So if domestic vinegar is somewhere between 5 (regular white vinegar) and 7% (pickling vinegar) by volume,  then 3 M vinegar would be between 15 and 21%. Very unscientific calculation there, but perhaps close enough for these purposes.

In what I thought was a rather spectacular example of greenwashing, you can get Eco Living Solutions brand 25% industrial grade acetic acid on that South American River website. 45 and 75% also appeared to be available in different brands, I just thought the marketing on that one was hilarious. 

[High Bridge Pottery]

On 11/24/2022 at 2:21 PM, High Bridge Pottery said:

Never did any working out for how much more the glaze costs so maybe that will make things look worse but hopefully it is such a small % total it doesn't make much difference.

I made this comment in my first post but never really followed it up and I was certainly way off in my estimations of how much glaze impacts the cost. I did a little searching today and the only figures I could find were 10-20% of the bisque weight is the weight of glaze applied. I will have to test my own work but I thought it would be a lot less.

I did a quick search for a stoneware recipe that had 25% of Kaolin, Ball clay, Feldspar and silica which came out to £1.20 a kg. I did use £1 per kg in the first calculation but changed to the £1.20 value here, I kept the total weight of ware as 4.5kg in the kiln and £3 extra for a cone 10 firing vs cone 03. I also looked back through some of my cone 10 glaze recipes that varied from £2-4 per kg so went with the lower estimate for the calculations. It seems even with 5% of the bisque weight being added as glaze you are still coming close to 10% of the cost for cone 10 and 20% of the cost for cone 03. That goes up to 25% and 50% respectively for 20% glaze.

Once I get over 10% it starts becoming more expensive firing to cone 03 than to cone 10. Your prices and kiln efficiency may vary, frits seem to cost at least double in the UK compared to USA.

Cone 10 clay - £1.20 per kg. Cone 10 glaze - £2 per kg.

Cone 03 clay -£1.35 per kg. Cone 03 glaze - £6.35 per kg.

Edited February 27, 2023 by High Bridge Pottery

[Min]

3 hours ago, High Bridge Pottery said:

I made this comment in my first post but never really followed it up and I was certainly way off in my estimations of how much glaze impacts the cost. I did a little searching today and the only figures I could find were 10-20% of the bisque weight is the weight of glaze applied. I will have to test my own work but I thought it would be a lot less.

10 - 20% of the weight of a pot is glaze seems really high to me too. I have a glaze firing starting later today, I will weigh a test tile or two and then glaze and reweigh it after firing. Rest of the pots are already glazed or else I would do some of those.

[High Bridge Pottery]

I want to figure out how much dry glaze is on the bisque so not sure you need to fire it. After posting I went and glazed one of my test glaze towers seen in a previous post. Went for the most extreme and did a 6 second dip on the outside and then poured the inside and let that sit for 6 seconds before pouring out. It's been sat on a warm radiator since then so it must be pretty dry by now but I will double check the weight tomorrow. Haven't quite narrowed down the recipe yet so no big batch to test larger items.

Bisque tower - 10.165g

Bisque tower with glaze - 11.795g

and a difference of 1.63g

 

Doing 1.63 / 10.165 x 100 gives me 16.04% 

 

I will try another one now with a normal 2 second dip and pour and see how that changes the %. Not sure why I didn't do that as well in the first place.

Edited February 27, 2023 by High Bridge Pottery

[Bill Kielb]

50 minutes ago, High Bridge Pottery said:

and a difference of 1.63g

How much of that is water? Maybe not a bunch…..

[neilestrick]

4 hours ago, High Bridge Pottery said:

Once I get over 10% it starts becoming more expensive firing to cone 03 than to cone 10.

There are other cost savings with firing to lower temps besides just the cost of electricity, big time if you're firing to cone 10 in the electric kiln.

- Extended element life. Firing just 04 will give you 2-3x the element life versus glazing at 5/6, double that vs cone 10.

- Longer kiln life

- Longer kiln furniture life

- Less energy removing excess heat from the studio (if you're running AC or fans)

Plus you can increase output with shorter firing schedules, and it's better for the planet.

[High Bridge Pottery]

8 minutes ago, Bill Kielb said:

How much of that is water? Maybe not a bunch…..

It had been sat on a radiator for about 3 hours before I weighed it, although the heating wasn't on for all of that time. The clay is pretty thin (1.5-2mm) so that it probably skewing the data somewhat and making it look worse than it is. 

3 minutes ago, neilestrick said:

There are other cost savings with firing to lower temps besides just the cost of electricity, big time if you're firing to cone 10 in the electric kiln.

- Extended element life. Firing just 04 will give you 2-3x the element life versus glazing at 5/6, double that vs cone 10.

- Longer kiln life

- Longer kiln furniture life

- Less energy removing excess heat from the studio (if you're running AC or fans)

Plus you can increase output with shorter firing schedules, and it's better for the planet.

If I can get 4-6x the element life then that will certainly add up  I wasn't sure how to calculate the savings with elements and kiln life so just left them out of the equations for now but reading your post it seems I will save more than I thought.

[Min]

Are the figures of 10-20% for thinly cast wares, thrown pots, sculpture or just a general average?

[neilestrick]

3 hours ago, High Bridge Pottery said:

If I can get 4-6x the element life then that will certainly add up  I wasn't sure how to calculate the savings with elements and kiln life so just left them out of the equations for now but reading your post it seems I will save more than I thought.

Firing to cone 10 is really the worst thing you can do to your kiln in terms of longevity. Elements in the US are currently about $350 a set (6 elements, sale price) so you could save $3-4 per firing on element costs. Relays will last longer since they'll cycle less and be exposed to a lot less heat. The bricks will definitely last longer since you won't be firing them past their actual temp rating (2300F).

[High Bridge Pottery]

45 minutes ago, Min said:

Are the figures of 10-20% for thinly cast wares, thrown pots, sculpture or just a general average?

I found this statement here - https://www.oldforgecreations.co.uk/blog/pricing-your-pottery

" To calculate the weight of glaze - weigh a dry piece before you glaze it, glaze it as normal, leave it to dry fully, weigh it again. The difference is the glaze weight. If you can't be bothered, just assume it's a fraction of the clay weight. 10-20% should do it."

So it's not really that specific or accurate  but I couldn't find anything else giving any better ideas.

 

Maybe it is better to think about surface area than weight of the bisque, I did just find this talking about spraying glaze - https://digitalfire.com/4sight/datasheets/GlazeSprayingForCraftPotter.pdf

"Now the second thing you need to measure, is how much glaze is appropriate for a given area of pot. This is easiest to explain with an example. One much-used glaze is a dark rich temmoku which we mix to SG=1.4 , at which it is just right for dipping mugs and bowls and such. After spraying this glaze umpteen times onto various pots (chiefly big platters and casseroles, not convenient to dip) we’ve decided that 10 mL of this glaze is just right for an area of 100 square centimetres"

 

I guess that means for 100 square centimeters they are using 6.5-7g of dry glaze. If we have a cylinder 8cm diameter and 10cm height and pretend the inside has the same surface area as the outside that make ~700cm2 and 45.5g of dry glaze. Could probably make a mug that size from 500g/1lb of clay maybe a bit more so it still seems around 5-10% of the weight of bisque could be used to estimate dry glaze.

 

[Callie Beller Diesel]

Joe at Old Forge does mention that his spreadsheet is meant to help with pricing/earning calculations. Using his “lazy” method of the assigned, and probably padded value in that instance will factor for things like the extra amount you need to be able to dip a piece, glaze waste, testing, etc. 

When I used the Brongniart calculator to figure out the dry weight of 10 ml of a glaze with sg 1.4, I got 4.6g. That value won’t be super accurate for you because your frit use means the calculator’s default dry weight value is off. But it all depends on how accurate you want/need to be.

Joe’s weighing method is going to be the most straightforward tool for measuring exactly what’s used on a given piece.

[High Bridge Pottery]

1 hour ago, Callie Beller Diesel said:

When I used the Brongniart calculator to figure out the dry weight of 10 ml of a glaze with sg 1.4, I got 4.6g.

This one? https://pietermostert.github.io/SG_calc/html/brongniart.html it gives me 6.5g as the answer. If it's a sg of 1.4 then 10ml should weigh 14g? and 10ml of water is 10g? I use the post on clay art so (14-10) x 5/3 = 6.667 Unless I am wrong about the glaze weighing 14g.

 

I tested the glazed bisque again this afternoon and got 7.25% of bisque weight for a 2 second dip and 14.75% for the 6 second dip. Some off the loss from my previous value in % of the 6 second may be from touching it and a bit of water as my glaze is a little dusty on the surface and comes off easily.

I would be interested if anybody wants to try out weighing bisque then glazing and drying to see what values they get.

 

Finally got some HCl to try dissolving these crystals, just got to work out how to dry and weigh again after sitting in HCl as I am assuming it wont all dissolve. Need to read about safety and disposal, guess I should neutralise it before disposal and figure out a way to catch the crystals again. I don't want to ruin the mesh in my sieve so maybe coffee filter paper.

Edited February 28, 2023 by High Bridge Pottery

[Callie Beller Diesel]

Yep, that calculator.

You’re right. I was using volume measurement of 10 in the first box, not weight. (Facepalm)

You can neutralize muriatic acid with some bicarb or diluted ammonia, and might be good to keep some handy while working with it. For disposal, you’d have to check with whoever deals with household chemical disposal locally. Where would you drop off things like used paint thinner?

[High Bridge Pottery]

Once it's neutralised with bicarb isn't it fine to pour down the sink as it's just salty water?

[Min]

Test tile weight results on 2 test tiles about the same thickness as my pots, maybe a tiny bit thicker.

1 - bisque weight 48.51 grams, weight just after dipping 53.39, fired weight 50.86

2 - bisque weight 54.97 grams, weight just after dipping 61.80, fired weight 58.32

sg of glaze 1.50, this glaze needs a heavy application to develop microcrystalline finish. 
Glaze LOI is 6.50

Yup, salty water and CO2.

[High Bridge Pottery]

Thank you for sharing. Doing the maths and either pretending the water doesn't exist in the weight after dipping or assuming the bisque weight it the same as fired clay weight and LOI is 6.5% you are somewhere in between 5-10% dry glaze for the weight of bisque. I always felt it would be 1% or less but never ran any tests to prove that to myself before now. I think for a glaze that could be thinner maybe 3% is the lower limit.