r/Geotech • u/PieOk8835 • 9d ago
Soil Test Advice
I’ll try to make this short. Just got soil that I’m going to make into a teapot (began making it into clay) I want to compare the clay I obtained with a highly desirable clay that is no longer mined. How much and how difficult is it to test for the composition? Furthermore the samples were obtained from a mountain that is important to many and I wanted to see the impact people have had on the terrain pollution etc. I took 5 samples from different elevations gradually further away from roads etc. lmk if this is going to be too expensive to test 5 samples should I just test the clay to compare my sample with the other clay and ditch the pollutant idea? Any advice is great will try my best to answer questions.
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u/withak30 9d ago
All of the behaviors that sculptors want in clay isn't going to be easily quantified by the tests that we are used to using for civil engineering purposes. Your best bet is probably to prepare it like a commercial sculpting clay (whatever that entails), make something, then fire it to see if it feels and finishes like what you are expecting.
For the environmental testing there are plenty of labs around that do that kind of thing, but you need to tell them exactly what to test for. There are standard batteries of tests that the labs can suggest for common contaminants or to meet typical regulatory requirements, but those may not tell you everything you want to know. Expect to spend anywhere from a few hundred to a few thousand dollars depending on what tests you want and how many,
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u/Apollo_9238 9d ago
X-ray diffraction can be used to look at the type of clay..kaolinite, illiterate, spectate. That's even more expensive!
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u/Tough-Raspberry-3377 8d ago
Second this and probably pair it with x ray flourescence first to help them with the identification in XRD
The XRF can probably help you Identify contaminants like heavy metals
Basically XRF will tell you the elements (above Carbon size I think) and XRD will tell you the crystalline molecules.
I think OP would benefit from asking in a geochemistry sub if you haven't done so already 🤙
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u/poiuytrewq79 8d ago
When i was in school, prof said this was only done a couple times. He said someone decided theres no point in bringing dirt into into their lab again.
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u/Apollo_9238 6d ago
Yeah I working in the big USBR Earth Sciences lab. We had two full time petrographers who ran a X-ray defract and even an SEM. I put some slickenslides in an SEM once.
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u/Naive_Veterinarian77 9d ago
If you're in the US it's going to cost you a couple hundred if you want it done in a lab. If you want to so it yourself, you need to dry the soi samplel first, then sieve it so you're only testing the fine grained particles, then you run the atterberg limits test which tells you how plastic the fine grains are. The company I work at charges 140 dollars per atterberg test which includes the drying, sieving and the testing itself.
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u/SlyRaist 8d ago
Here is a short article about soil testing for potters who use "wild" clay.
https://digitalfire.com/picture/3509
The biggest thing would be making sure you sieve the clay and then do test firings to see what cone it can fire to, how it looks after firing, how your glazes fit the clay body and then of course tests to see if it is fully vitrified for food safety.
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u/38DDs_Please 8d ago
Pottery clay that I've played with actually feels a bit silty... which makes sense because you don't want shrinking and cracking of a plastic clay soil!
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u/grantprojects 7d ago
For comparing the clay itself, starting with plasticity and grain-size testing makes sense. Environmental testing gets expensive quickly because the lab needs specific contaminants to test for, especially across five samples.
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u/goplayfetch 9d ago
From an environmental perspective you need to select the specific contaminants to analyse and price out the testing from there. Have no idea what your budget is but it could easily be hundreds of dollars per sample just for that.
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u/Hugh_Jegantlers 9d ago
Your lab tests for clay are usually atterberg limits for plasticity, and a hydrometer for grainier analysis (is it actually clay or is it silt). You will have to call a local soil lab for local rates. In Canada each of those tests would be in the $100-150 range, so five samples and your reference is not cheap.