A most enjoyable video, and really splendid to see the Roman style kiln in action. It looked very efficient and it was impressive to see how many pots could be packed into it.
I've started a bit of a side hobby over the winter in learning everything that interests me about pottery from ancient to modern methods as the artistry has its own appeal, though for me, it's also in experimenting with the chemistry to see what I can make apply to other projects. In happenstance as it goes, I was watching a video on Tierra Negra the other day, and the method they use to go from the iron oxide slip color to black was adding green herbs and native grasses right at the end of the firing and sealing it into their kilns (some were quite large, dedicated structures, though others did small batches in oil drums, sealing them via the lids with the green grasses in at the lull of firing). Not sure how universal that would work with this style firing, but might be worth an experiment if adding a variated depth of green wood would assist in blackening the pottery. As I understand it, you're wanting the carbon to travel up into your chamber without further combustion to act as a topical coating, which even when coming down from 800-900*C would be a large ask without the proper reduced or neutral gas mix already sequestered inside.
Hi, the technique of producing black pottery using organics in low temperature firings is quite common the world over, but as you say, even at temperatures below 900C the intense reduction needs to be maintained while the kiln cools below about 500C. It relies for its colour on both trapped carbon and on conversion of the iron in the clay from a ferric to a ferrous oxide. Roman grey and black burnished wares make use of this technique. Terra negra (Black Samian) and Colour Coated wares on the other hand trap the black iron in a sintered or semi fused slip, achieved at considerably higher temperatures.
@@PottedHistory hey just wanted to add a thought, I have been experimenting with ancient pottery replication specifically southwestern United States before 1200 AD. If you want black pots, try slipping the pot with iron hemitite or limonite , body clay, and sodium, soda ash works well. It’s possible they used potash but soda ash is more reliable at primitive temps. After a few years research I’m convinced many ancient cultures used soluble salts in pottery. But I digress 🙂 cheers!
Thanks @@coopart1 , I'd agree, we use Soda Ash and various iron oxides including haematite, magnetite in the form of hammer-scale, yellow ochre and iron slag to make samian terra sigillata slip and Nene Valley colour coated wares. Black burnished ware on the other hand, was made simply in the reducing atmosphere of the kiln without additional slip. Like you we've experimenting for some time with materials that would have been available to the Romans, soda ash is the perfect combination of a flux and a deflocculent.
Thanks Tiberiotertio , I think this type of kiln was pretty widespread for making coarse wares, of course in places like Rheinzabern and Graufesenque, there were also more complex kilns used in the Terra Sigillata industry.
No, it's VERY different with a kiln, you have to be constantly in front of the fire, stoking and raking, the firebox gets up to temperatures of 1300C, and the radiated heat at a metre distance (where you have to work to do this) has been measured between 400C & 500C, hot enough to not only roast meat but burn it. This is the whole point of experimental and experiential archaeology, we learn from the experience. We also fire many prehistoric style open "bonfire firings", the temperatures are much lower and we only occasionally have to get close to the fire.
Really amazing and instructive. I fire my earthenware in a smaller kiln very similar to that. I am just wondering whether blacks would've been achieved by sealing the kiln at a lower temperature.
You're right that it can be better to allow it to cool a little before the final stoking and sealing. I think we were all feeling pretty tired and I made the decision to finish.
Really enjoyed watching this, fascinating to think that this was going on in Roman times. Would the Romans have only fired the pots once to that temperature? Did they have a way to seal them to stop liquids from leaching out?
Thank you for this video. It's very informative and easy to follow. What Roman Pottery site do you know near Newark? I'm from the area and don't know of one.
Great video! I’m curious what you used for the bars in the fire box and the chamber floor? We have a similar kiln we have been building (not authentic at all) and we’re thinking of using rebar but we’re concerned with sagging after several uses. I would like to use something different, and I obviously haven’t researched this design enough. Thanks so much for sharing your video.
Hi Brenton, you can certainly formulate glazes that would work in this kiln, although because of the wide temperature variation it would need to have a wide maturing range. The Romans did fire glazed pots and obviously slip coated wares like Terra Sigillata, but these would have been fired in a more sophisticated kiln such as those excavated on the Continent.
HI all. Really wonderful to see an ancient style kiln firing. What is the final temp reached. I use F but can convert C to F. Thank you for sharing. Its truly inspirational.
I’ll withdraw my question about the bars now that I’ve watched the video again with good audio and you described the bars as fired clay. As for not a roving the black finish, could it just be a factor of not enough I burned fuel put in the box before sealing so that it used up the oxygen before running out of fuel? (Or the air leak as you mentioned. ) I look forward to more of your fantastic videos.
Hi Eric, no problem about the bars. In fact I've seen several excavated Roman kilns, where the only clay available for the bars would have been the same as the potting clay they were using, and as such, not being very refractory the bars have, as you say, bent after several firings. Rotating the bars after each firing would prolong their life, but I thing that Roman potters accepted that kiln furniture was expendable to some degree. As regards the oxidation of the firing, we've had good black reduction with similar quantities of fuel in the past. I do think that an incomplete seal was largely to blame, mostly down to the fact that the kiln needs some serious maintenance at this stage. So really my own tardiness to blame. But I also think that waiting until the kiln had cooled a little more, before the final stoke, would have helped. Cooling reduction cycles are not uncommon in ceramics, more recent examples being 19th Century Lustre Ware.
@@PottedHistory thank you for the explanation of the bars. I’ll have to find out if there are any locations near us to dig some refractory clay to try. You’re probably familiar with the San Ildefonso black on black pottery from New Mexico. They have a nice history of beautiful pieces. It’s interesting to watch old film footage of Maria Martinez firing and then smothering with cow dung to get the reduction- if I remember it correctly.
@@eric8527 Maria Martinez has been one of my pottery icons since I was a student back in the 1970s. Her work, especially the black on black, is stunning. Brought to the attention of a British audience by Bernard Leach among others. Good luck with the clay.
Actually it's a delicate balance: some level of hot embers will help by preheating the air entering the firebox. Too meny embers will consume the oxygen entering the kiln and cause a drop in temperature.
Not entirelt sure what you mean John. It does consume oxygen but not at such a rate as to need us out of the way of the air flow, nor so much that it renders the atmosphere unbreathable.
@@johnbooth1110 Ah, that's a very different beast John, I used to fire a 120cu ft wood fire and a 180cu ft diesel stoneware kiln to 1320C. A Roman kiln fired to 1000C is much less challenging.
Instead of using good new pots to support the center if you made some clay columns. That would prevent you from getting any pressure cracks in the pots.
Given the amount of fuel, time, and arduous work required for each firing, every bit of packing space within the kiln is a valuable commodity - a commodity of production capacity that would be wasted if filled up with support structures having no value after the firing.
Palestinian kilns used olive stones up until the 1960's. Then car tyre inner tubes proved a free and energy dense fuel. Pine cones? Wood is a premium resource in the Med region.
Thanks Mark, olive stones I haven't seen as a fuel, a new avenue for research. I'd be really interested to see how they stoked with them. Chaff for instance, has to be wafted into the kiln atmosphere one shovelful at a time. You're right about timber being at a premium, as I say with the Vindolanda kiln, roman potters would not be splitting logs, their fuel would have been coppice, brash, gorse or hedgerow material. The only reason that we do, is that this is the material that we have available to us.
I think you let the clay to fire too much, this technique is used in Spain and you ought to be carefull with the temperature as well as the fast cooling process, it needs to be open if you want blackware
You've got it backwards. Black ware is caused by a lack of oxygen in the kiln. Opening the kiln up would cause the iron in the clay to turn bright red. Sealed kilns make black pots.
On the "they probably werent naked like they are depicted, it's probably a religious thing" point: I think it's too often a default assumption to make. I have worked a lot in my youth burning large amount of branches outside after chopping down trees with my father. He was chopping, I was in charge of burning the branches. It makes a large, very hot bonfire. Think a couple meters diameter. To get anywhere near it is impossible. No clothes help you, if anything you are just sweating less efficiently because of them. What I would often do, is set the bonfire next to the nearby lake, take a dip in the water, and I could comfortably stoke and arrange the fire while wet. For a couple minutes I was invulnerable to it. You can imagine waterlogged clothes would slow you down too much, but while naked, you get just enough time to sort the fire out without getting a heatstroke.
Water soaked clothes would actually boil you, and seriously scald your skin. The fire in the firebox can reach temperatures of up to 1300C and the radiated heat can be in excess of 500C at a metre distance, focussed by the narrow firemouth. Bonfires rarely exceed 800C with most of the heat carried upwards . To stoke and rake out a kiln of this type it is necessary to get very up-close and personal. We are firing the Vindolanda Kiln tomorrow and I will try to take some temperature readings in front of the firebox I am approaching 70, I have been a potter all my working life, and I fired my first wood fired kiln in my teens, I do know what I'm talking about.
well done to everyone, narration was perfect :)
Wonderful demonstration - Bravo!
Fascinating
A most enjoyable video, and really splendid to see the Roman style kiln in action. It looked very efficient and it was impressive to see how many pots could be packed into it.
Thanks Peter, yes visitors are always amazed how many pots come out of what appears to be a rather small kiln.
Really enjoyed this video. Thanks for uploading!
Thanks Ross. Glad you enjoyed it!
I've started a bit of a side hobby over the winter in learning everything that interests me about pottery from ancient to modern methods as the artistry has its own appeal, though for me, it's also in experimenting with the chemistry to see what I can make apply to other projects. In happenstance as it goes, I was watching a video on Tierra Negra the other day, and the method they use to go from the iron oxide slip color to black was adding green herbs and native grasses right at the end of the firing and sealing it into their kilns (some were quite large, dedicated structures, though others did small batches in oil drums, sealing them via the lids with the green grasses in at the lull of firing). Not sure how universal that would work with this style firing, but might be worth an experiment if adding a variated depth of green wood would assist in blackening the pottery.
As I understand it, you're wanting the carbon to travel up into your chamber without further combustion to act as a topical coating, which even when coming down from 800-900*C would be a large ask without the proper reduced or neutral gas mix already sequestered inside.
Hi, the technique of producing black pottery using organics in low temperature firings is quite common the world over, but as you say, even at temperatures below 900C the intense reduction needs to be maintained while the kiln cools below about 500C. It relies for its colour on both trapped carbon and on conversion of the iron in the clay from a ferric to a ferrous oxide. Roman grey and black burnished wares make use of this technique. Terra negra (Black Samian) and Colour Coated wares on the other hand trap the black iron in a sintered or semi fused slip, achieved at considerably higher temperatures.
Wow this to me is very impressive , love it , great job everyone .
Thank you, much appreciated.
excellent video
super cool awesome to see great work
Thank you!
Very interesting! So cool!
Wonderful ! Thanks for sharing this experience
Our pleasure! Thanks for your comment.
@@PottedHistory hey just wanted to add a thought, I have been experimenting with ancient pottery replication specifically southwestern United States before 1200 AD. If you want black pots, try slipping the pot with iron hemitite or limonite , body clay, and sodium, soda ash works well. It’s possible they used potash but soda ash is more reliable at primitive temps. After a few years research I’m convinced many ancient cultures used soluble salts in pottery. But I digress 🙂 cheers!
Thanks @@coopart1 , I'd agree, we use Soda Ash and various iron oxides including haematite, magnetite in the form of hammer-scale, yellow ochre and iron slag to make samian terra sigillata slip and Nene Valley colour coated wares. Black burnished ware on the other hand, was made simply in the reducing atmosphere of the kiln without additional slip. Like you we've experimenting for some time with materials that would have been available to the Romans, soda ash is the perfect combination of a flux and a deflocculent.
Great video and narration
Thanks Jakob 😁
Reminds me of the original Roman kilns I have seen in Rheinzabern.
Thanks Tiberiotertio , I think this type of kiln was pretty widespread for making coarse wares, of course in places like Rheinzabern and Graufesenque, there were also more complex kilns used in the Terra Sigillata industry.
Great video! So interesting to see the process and thre final result! Thank you! Cheers from Finland!
Glad you enjoyed it! Always nice to hear that we are reaching viewers in other parts of the world.
No, it's VERY different with a kiln, you have to be constantly in front of the fire, stoking and raking, the firebox gets up to temperatures of 1300C, and the radiated heat at a metre distance (where you have to work to do this) has been measured between 400C & 500C, hot enough to not only roast meat but burn it. This is the whole point of experimental and experiential archaeology, we learn from the experience. We also fire many prehistoric style open "bonfire firings", the temperatures are much lower and we only occasionally have to get close to the fire.
Wonderful❤
Thank you!
Really amazing and instructive. I fire my earthenware in a smaller kiln very similar to that. I am just wondering whether blacks would've been achieved by sealing the kiln at a lower temperature.
You're right that it can be better to allow it to cool a little before the final stoking and sealing. I think we were all feeling pretty tired and I made the decision to finish.
Really enjoyed watching this, fascinating to think that this was going on in Roman times. Would the Romans have only fired the pots once to that temperature? Did they have a way to seal them to stop liquids from leaching out?
Thank you for this video. It's very informative and easy to follow.
What Roman Pottery site do you know near Newark? I'm from the area and don't know of one.
Great video! I’m curious what you used for the bars in the fire box and the chamber floor? We have a similar kiln we have been building (not authentic at all) and we’re thinking of using rebar but we’re concerned with sagging after several uses. I would like to use something different, and I obviously haven’t researched this design enough. Thanks so much for sharing your video.
What are the sides of the kiln made from? Thank you!
Basically mud! I will post the video of the kiln construction some time soon.
@@PottedHistory thank you!
Amazing video. Do you think the kiln gets hot enough to fire glazes?
Hi Brenton, you can certainly formulate glazes that would work in this kiln, although because of the wide temperature variation it would need to have a wide maturing range. The Romans did fire glazed pots and obviously slip coated wares like Terra Sigillata, but these would have been fired in a more sophisticated kiln such as those excavated on the Continent.
HI all. Really wonderful to see an ancient style kiln firing. What is the final temp reached. I use F but can convert C to F. Thank you for sharing. Its truly inspirational.
I think that 958C was the top temperature.
I’ll withdraw my question about the bars now that I’ve watched the video again with good audio and you described the bars as fired clay.
As for not a roving the black finish, could it just be a factor of not enough I burned fuel put in the box before sealing so that it used up the oxygen before running out of fuel? (Or the air leak as you mentioned. )
I look forward to more of your fantastic videos.
Hi Eric, no problem about the bars. In fact I've seen several excavated Roman kilns, where the only clay available for the bars would have been the same as the potting clay they were using, and as such, not being very refractory the bars have, as you say, bent after several firings. Rotating the bars after each firing would prolong their life, but I thing that Roman potters accepted that kiln furniture was expendable to some degree. As regards the oxidation of the firing, we've had good black reduction with similar quantities of fuel in the past. I do think that an incomplete seal was largely to blame, mostly down to the fact that the kiln needs some serious maintenance at this stage. So really my own tardiness to blame. But I also think that waiting until the kiln had cooled a little more, before the final stoke, would have helped. Cooling reduction cycles are not uncommon in ceramics, more recent examples being 19th Century Lustre Ware.
@@PottedHistory thank you for the explanation of the bars. I’ll have to find out if there are any locations near us to dig some refractory clay to try.
You’re probably familiar with the San Ildefonso black on black pottery from New Mexico. They have a nice history of beautiful pieces. It’s interesting to watch old film footage of Maria Martinez firing and then smothering with cow dung to get the reduction- if I remember it correctly.
@@eric8527 Maria Martinez has been one of my pottery icons since I was a student back in the 1970s. Her work, especially the black on black, is stunning. Brought to the attention of a British audience by Bernard Leach among others. Good luck with the clay.
@@PottedHistory I’m sorry I missed this last message, thank you.
as blacksmith might need to get me a vulcan drinkig cup or jugg it all looks good
keeping a bed of hot ashes in the front fire box helps raise the temperature
Actually it's a delicate balance: some level of hot embers will help by preheating the air entering the firebox. Too meny embers will consume the oxygen entering the kiln and cause a drop in temperature.
wood fired kilns . will as they are fired sux oxygen around the kiln, always helps to step away from the firebox,
Not entirelt sure what you mean John. It does consume oxygen but not at such a rate as to need us out of the way of the air flow, nor so much that it renders the atmosphere unbreathable.
@@PottedHistory i had a 27 cubic feet kiln , 15 hours firing . when firing stay at least 3 feet away from the kiln face. while in reduction,
@@johnbooth1110 Ah, that's a very different beast John, I used to fire a 120cu ft wood fire and a 180cu ft diesel stoneware kiln to 1320C. A Roman kiln fired to 1000C is much less challenging.
Instead of using good new pots to support the center if you made some clay columns. That would prevent you from getting any pressure cracks in the pots.
True but thw cracks are a rare occurrence so worth the risk
And there is not really any archaeological evidence for such supports.
Given the amount of fuel, time, and arduous work required for each firing, every bit of packing space within the kiln is a valuable commodity - a commodity of production capacity that would be wasted if filled up with support structures having no value after the firing.
Palestinian kilns used olive stones up until the 1960's.
Then car tyre inner tubes proved a free and energy dense fuel. Pine cones? Wood is a premium resource in the Med region.
Thanks Mark, olive stones I haven't seen as a fuel, a new avenue for research. I'd be really interested to see how they stoked with them. Chaff for instance, has to be wafted into the kiln atmosphere one shovelful at a time. You're right about timber being at a premium, as I say with the Vindolanda kiln, roman potters would not be splitting logs, their fuel would have been coppice, brash, gorse or hedgerow material. The only reason that we do, is that this is the material that we have available to us.
I think you let the clay to fire too much, this technique is used in Spain and you ought to be carefull with the temperature as well as the fast cooling process, it needs to be open if you want blackware
No, we have successfully fired black Ware on several occasions, but didn't get the seal tight enough this time.
You've got it backwards. Black ware is caused by a lack of oxygen in the kiln. Opening the kiln up would cause the iron in the clay to turn bright red.
Sealed kilns make black pots.
On the "they probably werent naked like they are depicted, it's probably a religious thing" point: I think it's too often a default assumption to make. I have worked a lot in my youth burning large amount of branches outside after chopping down trees with my father. He was chopping, I was in charge of burning the branches. It makes a large, very hot bonfire. Think a couple meters diameter. To get anywhere near it is impossible. No clothes help you, if anything you are just sweating less efficiently because of them. What I would often do, is set the bonfire next to the nearby lake, take a dip in the water, and I could comfortably stoke and arrange the fire while wet. For a couple minutes I was invulnerable to it.
You can imagine waterlogged clothes would slow you down too much, but while naked, you get just enough time to sort the fire out without getting a heatstroke.
Water soaked clothes would actually boil you, and seriously scald your skin. The fire in the firebox can reach temperatures of up to 1300C and the radiated heat can be in excess of 500C at a metre distance, focussed by the narrow firemouth. Bonfires rarely exceed 800C with most of the heat carried upwards . To stoke and rake out a kiln of this type it is necessary to get very up-close and personal. We are firing the Vindolanda Kiln tomorrow and I will try to take some temperature readings in front of the firebox I am approaching 70, I have been a potter all my working life, and I fired my first wood fired kiln in my teens, I do know what I'm talking about.