Geologists! Potters! Brickmakers! I need natural clay help!
February 26, 2021 1:29 PM Subscribe
I'm interested in harvesting natural clay for a number of projects and have questions about Southern Indiana and geology resources.
I'm interested in harvesting natural clay for making bricks, pottery, and tiles. I am going to be doing some experimenting this year and next and hope to have things rolling.
My main question - is there a resource that I can use to identify clays (especially in Southern Indiana) that is more approachable than what I am finding? I've got access to what I understand to be good clay, but I'd like to be able to understand it better before I just start making stuff and experimenting.
I've been able to find academic and scientific information, but there isn't a middle of the road option I've found. It is either "to harvest clay, dig around and purify like this!" OR "deposits in the Mississippian strata can be defined in relation to the crystal structure of the secondary formation of silica as referenced in the tertiary layer of shale sediments...*"
I can work with either of these and get through the second one with lots of googling, but the technical papers and geological details can be overwhelming for an amateur who just wants to know if this white and sky blue clay is bentonite or what you call the yellow and white clay 4 feet down.
I think what I am looking for is an approachable way to identify various clays in Southern Indiana (Spencer and Vanderburgh Counties specifically) and their potential uses, but I am coming up short.
What I am looking for is something that will tell me about the three types of clay I can frequently find, what they are called, and how to handle them for various uses. I've gotten through the first page or two of googling "Indiana clay and uses" and "Indiana geological clay survey" among other things and thought I'd ask here. Can anyone give me direction?
I'll reach out to local potters and ceramicists when I'm back home, but thought there would be some setup work I could read to prepare and understand better.
*This is geological gibberish, but hopefully it makes my point
I'm interested in harvesting natural clay for making bricks, pottery, and tiles. I am going to be doing some experimenting this year and next and hope to have things rolling.
My main question - is there a resource that I can use to identify clays (especially in Southern Indiana) that is more approachable than what I am finding? I've got access to what I understand to be good clay, but I'd like to be able to understand it better before I just start making stuff and experimenting.
I've been able to find academic and scientific information, but there isn't a middle of the road option I've found. It is either "to harvest clay, dig around and purify like this!" OR "deposits in the Mississippian strata can be defined in relation to the crystal structure of the secondary formation of silica as referenced in the tertiary layer of shale sediments...*"
I can work with either of these and get through the second one with lots of googling, but the technical papers and geological details can be overwhelming for an amateur who just wants to know if this white and sky blue clay is bentonite or what you call the yellow and white clay 4 feet down.
I think what I am looking for is an approachable way to identify various clays in Southern Indiana (Spencer and Vanderburgh Counties specifically) and their potential uses, but I am coming up short.
What I am looking for is something that will tell me about the three types of clay I can frequently find, what they are called, and how to handle them for various uses. I've gotten through the first page or two of googling "Indiana clay and uses" and "Indiana geological clay survey" among other things and thought I'd ask here. Can anyone give me direction?
I'll reach out to local potters and ceramicists when I'm back home, but thought there would be some setup work I could read to prepare and understand better.
*This is geological gibberish, but hopefully it makes my point
Try looking at the web soil survey for your area, here:
https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
It's a little clunky, but can give you a soil map of your area of interest (assuming it has been surveyed). You should understand that soil maps are not perfect, and only map to a certain "minimum making unit", so they are more about describing a farm-field sized area than any exact location. Still, see what the areas you are digging are mapped as, and then try searching for the name of that soil series. The description will give you a sample profile, i.e. what layers are at what depths, with what properties.
posted by agentofselection at 4:31 PM on February 26, 2021 [3 favorites]
https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
It's a little clunky, but can give you a soil map of your area of interest (assuming it has been surveyed). You should understand that soil maps are not perfect, and only map to a certain "minimum making unit", so they are more about describing a farm-field sized area than any exact location. Still, see what the areas you are digging are mapped as, and then try searching for the name of that soil series. The description will give you a sample profile, i.e. what layers are at what depths, with what properties.
posted by agentofselection at 4:31 PM on February 26, 2021 [3 favorites]
You could take a purely experimental approach to this problem and just dig up the clay you found and try forming and firing it. There are undoubtedly professional scientific methods of doing this, but what I'd do is form a number of pieces of identical size and weight, score them with marks like a ruler (and number each one with a unique number to keep track of how each is fired. Keep a notebook). Then I'd fire at different temps or cones in a test kiln. If you can throw, make cylinders or bowls of the same proportions and fire also, to check for slumping. You will then know the approximate properties of your clay, even if you don't know the exact composition. Expect quite a bit of shrinkage if there is no sand in the clay.
This is how potters have done it for centuries, and why potteries were historically located near clay deposits.
A good resource might be the archives of Ceramics Monthly, and they probably have a Q & A option on their website that might be able to answer you questions on using directly-dug clay. Along with lots of articles on ceramic artists they have columns on technical issues related to clays, glazes, and firing techniques. This sounds like a lot of fun!
posted by citygirl at 5:58 PM on February 26, 2021 [2 favorites]
This is how potters have done it for centuries, and why potteries were historically located near clay deposits.
A good resource might be the archives of Ceramics Monthly, and they probably have a Q & A option on their website that might be able to answer you questions on using directly-dug clay. Along with lots of articles on ceramic artists they have columns on technical issues related to clays, glazes, and firing techniques. This sounds like a lot of fun!
posted by citygirl at 5:58 PM on February 26, 2021 [2 favorites]
The answers to this question and the site archives might help.
posted by firstdrop at 8:56 AM on February 27, 2021 [1 favorite]
posted by firstdrop at 8:56 AM on February 27, 2021 [1 favorite]
My wife has many years of experience in clay and ceramics higher education. I read her your question as well as some of the responses and she had a few thoughts:
You may want to Google 'wild clay' and then perhaps see if you can find people who use wild clay in the areas you are considering. There might be clay artists in that area who use wild clay who would be willing to sell you small amounts to use, or who might offer advice. Also, 'wild clay' may lead you to resources for dealing with natural clay sourcing.
That being said, she estimated that production ceramic artists who use wild clay have to dedicate up to 1/3 or their production time to processing the clay. Say, two months out of a six month cycle. The link that firstdrop offers gives an idea of what is needed: multiple rounds of drying and sieving the clay to remove impurities. You need a professional respirator for this process, btw. I don't know what the threshold is for silicosis, but I do know that ceramic faculty of a certain generation succumbed to the disease from years of running a ceramics studio without proper ventilation and modern respirators.
There are natural clay veins that are fairly pure and that can be used with minimal or no processing. This is why North Carolina has Seagrove, for instance. Such veins may be a closely guarded secret however, because they are rare and valuable for their time savings. Native potters who have ancestral lands with pure clay deposits have considered such resources sacred and not to be used by outsiders.
She also wondered if you were considering wild clay for environmental reasons or sentimental reasons. If it's environmental reasons, art clay makes up less than 1% of clay commercially mined. If it's sentimental reasons, she suggested that you take a small amount from a riverbed in the region you are considering and see if it rolls into a tube. If it does, you have clay. Then incorporate that into commercial clay and you have that sentimental integration without respirators and months of processing. Any impurities in your small amount of riverbed clay will be spread thin across your commercial clay.
Lastly, we do know one clay company in the area - KY Mudworks in Louisville. You might reach out to them and see if they have any leads on wild clay from the region.
Good luck!
posted by Tchozz at 6:05 AM on February 28, 2021 [4 favorites]
You may want to Google 'wild clay' and then perhaps see if you can find people who use wild clay in the areas you are considering. There might be clay artists in that area who use wild clay who would be willing to sell you small amounts to use, or who might offer advice. Also, 'wild clay' may lead you to resources for dealing with natural clay sourcing.
That being said, she estimated that production ceramic artists who use wild clay have to dedicate up to 1/3 or their production time to processing the clay. Say, two months out of a six month cycle. The link that firstdrop offers gives an idea of what is needed: multiple rounds of drying and sieving the clay to remove impurities. You need a professional respirator for this process, btw. I don't know what the threshold is for silicosis, but I do know that ceramic faculty of a certain generation succumbed to the disease from years of running a ceramics studio without proper ventilation and modern respirators.
There are natural clay veins that are fairly pure and that can be used with minimal or no processing. This is why North Carolina has Seagrove, for instance. Such veins may be a closely guarded secret however, because they are rare and valuable for their time savings. Native potters who have ancestral lands with pure clay deposits have considered such resources sacred and not to be used by outsiders.
She also wondered if you were considering wild clay for environmental reasons or sentimental reasons. If it's environmental reasons, art clay makes up less than 1% of clay commercially mined. If it's sentimental reasons, she suggested that you take a small amount from a riverbed in the region you are considering and see if it rolls into a tube. If it does, you have clay. Then incorporate that into commercial clay and you have that sentimental integration without respirators and months of processing. Any impurities in your small amount of riverbed clay will be spread thin across your commercial clay.
Lastly, we do know one clay company in the area - KY Mudworks in Louisville. You might reach out to them and see if they have any leads on wild clay from the region.
Good luck!
posted by Tchozz at 6:05 AM on February 28, 2021 [4 favorites]
Response by poster: Thanks for the responses so far, everybody! I really appreciate it!
So it looks like the information I want is really distinct and separate between geologists/surveyists and the people who actually use the clays I am looking at. This is interesting because it means I may just have to write a book for myself connecting the two - or go back to school and get an MFA in pottery using this as a thesis.
For those interested in this specific question, and not to threadsit, I've found these links for the soil surveys:
https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/indiana/IN147/0/spencer.pdf
https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/indiana/vanderburghIN1976/vanderburghIN1976.pdf
Both of those are a good start. I am also just down the road from the old Uhl pottery, so this has started to be helpful as well: http://www.huntingburg.lib.in.us/UHLHistory1.html
So once this has all sorted itself out I'll post a resolution. I can't tell you how the direction has helped. I was all over the place, but am now a little more focused with some vocabulary and a better sense of things.
Tchozz, thank your wife wholeheartedly for me. I'm literally sitting on three different clay formations that have been used in the past for bricks and pottery. I'm harvesting bricks from a ruined 1850s homestead, need a few hundred more than are there, and would like to use the same clay that was used for the bricks that I understand were fired on-site. I've isolated the pit the clay was dug from and have been trying to differentiate between the layers 4-10 feet below the very thin and dubious topsoil. I've also isolated another clay vein under a very shallow coal deposit that locals have been telling me is amazing and can be used with minimal processing, but no one is a potter, so they are just going off of what their grandparents told them about it 70 years ago. The coal is useless as coal for a number of reasons, but the clay is beautiful raw. I think it is part of the same layer that the pottery I linked above used, but I've reached out to the county extension and other people connected with it to help me see what I have. Her direction really helped - I didn't realize that actually owning known veins was such a treasure, but the more I read since her comment, the more I understand and the more thought and care I will take in all this.
I also want to make roof tiles for outbuildings and other novelty things - flowerpots, &c. I need this to be as free as possible, with maybe my big expense building a backwoods on-site wood kiln that I already own 90 percent of the materials for. I know this was a done thing in the mid 19th century around my parts, I just need to put the pieces together and make the whole series of processes a little more understandable for me.
So off I go to experiment! You all are the best!
posted by Tchad at 8:52 AM on March 1, 2021 [3 favorites]
So it looks like the information I want is really distinct and separate between geologists/surveyists and the people who actually use the clays I am looking at. This is interesting because it means I may just have to write a book for myself connecting the two - or go back to school and get an MFA in pottery using this as a thesis.
For those interested in this specific question, and not to threadsit, I've found these links for the soil surveys:
https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/indiana/IN147/0/spencer.pdf
https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/indiana/vanderburghIN1976/vanderburghIN1976.pdf
Both of those are a good start. I am also just down the road from the old Uhl pottery, so this has started to be helpful as well: http://www.huntingburg.lib.in.us/UHLHistory1.html
So once this has all sorted itself out I'll post a resolution. I can't tell you how the direction has helped. I was all over the place, but am now a little more focused with some vocabulary and a better sense of things.
Tchozz, thank your wife wholeheartedly for me. I'm literally sitting on three different clay formations that have been used in the past for bricks and pottery. I'm harvesting bricks from a ruined 1850s homestead, need a few hundred more than are there, and would like to use the same clay that was used for the bricks that I understand were fired on-site. I've isolated the pit the clay was dug from and have been trying to differentiate between the layers 4-10 feet below the very thin and dubious topsoil. I've also isolated another clay vein under a very shallow coal deposit that locals have been telling me is amazing and can be used with minimal processing, but no one is a potter, so they are just going off of what their grandparents told them about it 70 years ago. The coal is useless as coal for a number of reasons, but the clay is beautiful raw. I think it is part of the same layer that the pottery I linked above used, but I've reached out to the county extension and other people connected with it to help me see what I have. Her direction really helped - I didn't realize that actually owning known veins was such a treasure, but the more I read since her comment, the more I understand and the more thought and care I will take in all this.
I also want to make roof tiles for outbuildings and other novelty things - flowerpots, &c. I need this to be as free as possible, with maybe my big expense building a backwoods on-site wood kiln that I already own 90 percent of the materials for. I know this was a done thing in the mid 19th century around my parts, I just need to put the pieces together and make the whole series of processes a little more understandable for me.
So off I go to experiment! You all are the best!
posted by Tchad at 8:52 AM on March 1, 2021 [3 favorites]
another clay vein under a very shallow coal deposit
My coal-mining-family grandfather called those clay veins seat earths, and wound up running a brick factory from one. The term was completely unfamiliar to my soil science prof ten years ago, but it might be useful in literature searches. (Seat earths are common IIRC because the hot wet weather that laid down what became coal accelerated the weathering of the land surface at the time - the right rocks, much weathered, become clay.)
posted by clew at 12:39 PM on March 1, 2021 [1 favorite]
My coal-mining-family grandfather called those clay veins seat earths, and wound up running a brick factory from one. The term was completely unfamiliar to my soil science prof ten years ago, but it might be useful in literature searches. (Seat earths are common IIRC because the hot wet weather that laid down what became coal accelerated the weathering of the land surface at the time - the right rocks, much weathered, become clay.)
posted by clew at 12:39 PM on March 1, 2021 [1 favorite]
This thread is closed to new comments.
posted by clew at 4:14 PM on February 26, 2021 [1 favorite]