Hi guys and welcome back to my channel, Blue Nose Trading. My name is Tori Solis, and today we are going to be going over the saturation coefficient of a clay body. The saturation coefficient, for me and why I went looking for it, answers the question "can this clay be outside during the winter in freezing conditions with ice without cracking?" This is super important to me because I make planters, and a lot of them may be subject to these kind of conditions. So I went on a grand search through the internet to figure out the answer to this question. I asked a few podcasts, and I could never really figure out a straight answer. A lot of people said that it came down to just straight "it's vitrified so it's safe". Which is true, but there's more.
The saturation coefficient is how much water the clay can absorb, and what space it leaves for the ice to expand when freezing. If it's within a certain range, allowing for this expansion of ice during freezing, then it should be considered safe for outdoor use.
We are going to break it down because it's math and math isn't always fun for everybody. I color coded the math. We are just going to take it one step at a time. If you want to learn a lot more about the science of how the saturation coefficient works, there is a great paper by Val Cushing on it from his notebook. Also, there is an entire article on digitalfire that goes over the same way, a little more detailed. I will link to digitalfire below and if I can find a link for the Val Cushing notes I will link to them, but I'm not sure if that's a thing. I'll figure it out.
We are going to be testing the saturation coefficient. The first thing that we are going to have to do is get the dry weight of these clay test tiles that have been fired to cone 6. Or whatever cone you're firing to. It doesn't really matter. Test it for how you would fire the clay, if you were firing it to finish for your own work. I fired to cone 6, so let's get testing.
V1: Dry Weight
Fired to final temperature.
Speckled buff: 36.21
B-mix: 39.73
Spectacular: 35.89
Loca mocha: 34.78
White stoneware: 26.54
Dragon fruit: 29.60
Trinity terracotta: 33.05
Frost: 40.03
We now need to prepare this clay for the immersion weight. We are going to do that by soaking it for 24 hours in water that is room temperature. After this clay has soaked for 24 hours, we're going to dry it off gently with a towel and weigh it again to get the immersion weight. Which will be V2 in our equation.
V2: Immersion Weight
Soaked 24 hours in room temperature water.
Speckled buff: 36.21
B-mix: 39.73
Spectacular: 35.89
Loca mocha: 34.78
White stoneware: 26.54
Dragon fruit: 29.60
Trinity terracotta: 33.05
Frost: 40.03
Next we're going to prep these tiles to calculate the boil weight. We are going to do this by boiling these tiles for three hours. Make sure that you keep an eye on these so that the water doesn't completely evaporate off of your pot.
After these have been boiled for three hours and sufficiently cooled with cool water so that you can touch them. Don't touch boiling things. We are going to gently dry them off on the surface with a towel. Then we are going to record the weight of them after they have been boiled for 3 hours.
V3: Boil Weight
Boiled for 3 hours.
Speckled buff: 36.21
B-mix: 39.73
Spectacular: 35.89
Loca mocha: 34.78
White stoneware: 26.54
Dragon fruit: 29.60
Trinity terracotta: 33.05
Frost: 40.03
Ok so we gathered all of our variables, with all our testing across several clay bodies. We have the dry weight, the immersion weight, as well as the boil weight all written down. But data doesn't really mean anything unless we do calculations. Now, I've color coded these, and we are going to plug these variables into these calculations so that we can get answers to our saturation coefficient.
For C, which is the 24 hour absorption. The 24 hour absorption equals the immersion weight minus the dry weight, and then that divided by the dry weight again. Now we just have to plug these in here to calculate C, the 24 hour absorption.
I just realized that I was converting these over to percentages, but for the sake of making our math easier, I am going to go ahead and leave them as decimals going forward for the rest of these calculations until the very end.
C: 24 Hour Absorption
C=(V2-V1)/V1
Speckled buff: (36.21-36.21)/36.21=.034
B-mix: (40.51-39.73)/39.73=.019
Spectacular: (37.74-35.89)/35.89=.052
Loca mocha: (35.51-34.78)/34.78=.021
White stoneware: (27.82-26.54)/26.54=.048
Dragon fruit: (30.43-29.60)/29.60=.028
Trinity terracotta: (33.31-33.05)/33.05=.008
Frost: (40.05-40.03)/40.03=.000
Now that we have the 24 hour absorption, which is C. We are going to calculate the boil absorption, which is going to be: boil absorption equal to boil weight minus the dry weight, divided by the dry weight. We are going to take that information from here and do those quick calculations down here.
B: Boil Absorption
B=(V3-V1)/V1
Speckled buff: (37.46-36.21)/36.21=.035
B-mix: (40.47-39.73)/39.73=.019
Spectacular: (37.81-35.89)/35.89=.053
Loca mocha: (35.46-34.78)/34.78=.020
White stoneware: (27.88-26.54)/26.54=.050
Dragon fruit: (30.48-29.60)/29.60=.030
Trinity terracotta: (33.29-33.05)/33.05=.007
Frost: (40.08-40.03)/40.03=.001
Now we know the variable that we have for C and the variables that we have for B. Now we have to move on to the second part of our calculation, which is actually calculating the saturation coefficient.
To test for the final calculation of the saturation coefficient, we have to take C, which is the 24 hour absorptions and divide it by B, which is the boil absorption. The saturation coefficient is equal to the 24 hour absorption divided by the boil absorption. We will go ahead and do all of those calculations very quickly.
S: Saturation coefficient
S=C/B
Speckled buff: .034/.035= .971
B-mix: .019/.019= 1
Spectacular: .052/.053= .98
Loca mocha: .021/.020= 1.05
White stoneware: .048/.050= .96
Dragon fruit: .028/.030= .93
Trinity terracotta: .008/.007= 1.14
Frost: .000/.001= 0
Let's go over what all of this means. There's two ways that your clay could be considered safe for outside. That is that the saturation coefficient, the number that we came up with in the end here highlighted in blue, is less than .78. So if the number highlighted in light blue is less than .78, that means this clay has enough room in it for expansion, a saturation coefficient that allows it to be safe for outdoor use. The only clay here that passed that particular test was the Laguna frost, porcelain, cone 6 porcelain. All of these others techincally would have got a failing grade for this particular variable. But, if the 24 hour absorption, or C, is less than 5%, then the clay is already safe for outdoor use. If you do these tests and you get C under 5%, then you know that your clay is safe to use outside in freezing conditions. If it's not, then you can continue to do the second test, find the saturation coefficient. Then, if the saturation coefficient is less than .78, then even though you have a high absorption, your clay is still safe for outside use.
Here, the only clay we have that wouldn't be safe for outside use during freezes in any circumstances would be the Trinity spectacular. It has a 24 hour absorption of 5.15%, and then it had a saturation coefficient of .98. So the saturation coefficient is too high to make it safe for freezing conditions, as well as the 24 hour absorption is too high to allow it to be safe for freezing conditions. But all of these other clay bodies: speckled buff, Laguna B-mix, loca mocha from Trinity, Trinity white stoneware, Industrial Minerals Company dragon fruit, Trinity terracotta and Laguna frost, they are all safe for outdoor use. It's been tested, we can confirm that now. You can do your own tests on your own clay bodies, so that you can come to your own conclusions. Or just to double check my math. I'm not a mathematician, there's a possibility that I made a mistake here. So I definitely encourage double checking and doing your own tests.
I'm going to be doing a series of work with some more fun clay bodies coming up this next year for 2023. I'm looking forward to it. We've got some New Mexico sandia red, I've also got some B3 black that I'm going to be playing with, and some Laguna azabache. I'm very excited about that. If you want to stay tuned for those upcoming series of work and overviews of those different clay bodies, be sure to subscribe to my channel, Blue Nose Trading. If you'd like to help support my channel, so that I can get access to different kinds of clay to use, or you just want to tell me about a clay that you think I should use, you should consider becoming a patron of my work at patreon.com/bluenosetrading.
Remember that you are very important and that you have some really great ideas. Make sure that you hang out and talk with your loved ones often, and I will see you guys next week.
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