Hi guys and welcome back to my channel, Blue Nose Trading. My name is Tori Solis, and today I'm going to be showing you how to test the absorption rate of your clay.
The absorption rate is also the "porosity", and this is how much water that your clay is able to soak up. This is kind of important for a few reasons. If your clay is too porous, and it's soaking up water, it can leak in all of the places where it's not glazed. Water can seep down through the foot ring, or up through the foot ring in certain situations. If the glaze that you are using is crazed at all, so it's cracked, it won't be creating a seal between the glaze, the outside and the clay, so water can seep through a a cracked glaze into a clay body sometimes.
There's a lot of different opinions on how low or high the absorption rate should be for a clay to be considered good to use for functional ware, like dinnerware. It really doesn't matter if you're doing sculpture so much. We'll make another video on parts that could matter for sculpture, but for right now, let's stay focused.
Clay companies will say that their are clays that are at 3% absorption, and that's fine to use. There are a ton of popular clay bodies fired to cone 6 that are around 3% absorption that plenty of people are using. Other people will try to stay below 2% absorption. Then there are a few people that swear, including the people at the Ceramic Materials Workshop, including Matt and Rose, that it should be as close to zero as possible, and at least less than .5%. I'm not here to join into the eternal argument of where your absorption rate should be. I'm only going to show you how to test it.
Today I'm going to be testing several different clay bodies. I'm going to be testing Industrial Minerals Company's Dragon fruit. I'm going to be testing Trinity Ceramics Terracotta fired at cone 6. These are all at cone 6 by the way. I'm going to be testing Laguna B-mix, Laguna Speckled buff, Trinity Ceramics White stoneware, Trinity ceramics spectacular, Trinity Ceramics Loca mocha, and Laguna Frost.
These are all clays that have been fired all the way to temperature. They are unglazed, and they have been fired to cone 6.
The first step here is to record the dry weight for each of the tiles. I put little codes on the back of my tiles to help keep things a little bit more organized for me. You go ahead and be organized or don't be organized. Whatever works best for you. Honestly only you are going to know how to best manage yourself and your space and time.
Next I'm going to put all of these tiles into this metal pan, and fill it with water. I'm not using a non-stick pan because these are going to bounce around and they might damage a non-stick pan. Just a fair warning.
I'm going to put this pot on the stove, turn it onto high. I also put a ton of water in here because this water needs to boil for the next two hours. After two hours we will be ready to cool them off with a little bit of cool-lukewarm water, so they are touchable.
Then I am going to take them and dry them off and put them on the table. We are going to need to re-weigh these again. This time we are taking the weight of them after they have been boiled for two hours to see how much of the water they absorbed. I did towel dry them first.
This is a moment of truth for a few of these clays. The clays that came from Trinity Ceramics, which is my local clay supply store, don't have their absorption rates listed online. So this is going to be really enlightening for me to learn what those absorption rates are.
Now that I have all their measurements, we are going to do the calculation here. We are going to take the weight boiled and divide it by the weight dry, and that is going to give us a one point some number, and the "point some number" is going to your percentage of absorption. I am just going to go down the list and calculate what we have going on here.
At the very end of this video I will have the results written down in text so you can check out the absorption rates of these. Some of them were quiet surprising, and some of them were not what I expected. Some were a little bit disappointing, but I'm still going to use some of those clays, but maybe change the way that I approach the work.
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Remember that you're important, you have great ideas, and I will see you next week.
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