I make those little earthenware Roman oil lamps, soaking in vegetable oil then baking in the oven at 4 or 500 degrees like cast iron pans. seems to seal them and give a glossy glazed look glazed look.

I recently had great success using powdered skim milk to seal a couple small drinking cups. I like using powered milk for a couple reason. 1. It is fat free and it's my general understanding that it is the proteins that bond with the clay to do the sealing. 2. It stores indefinitely if stored well in its dry form. 3. Its often cheaper than standard carton milk 4. You can mix as much or as little as you need (I made mine with double the powered called for in the directions. What I did for a process was find a plastic container with a lid that would hold my pieces and made enough milk to cover the pieces. I allowed them to stay in the milk over night in my refrigerator with the lid on the container. I then removed the pieces and removed all excess milk with a cloth and paper towel (mine had a thin white slime on there surfaces before wiping. I then placed them in my oven starting low around 200 degrees for a while to dry them. (Same as you would if you we're preheating greenware) Then I brought the temp up to say 300 for 20 min or so. Then up to 450-500 which is the max for my oven. Held this high temp for 15-30min then turned off the oven and allowed to cool. In my case I repeated this process because I didn't feel a had a complete seal after the first soak and bake. I was happy after the second time. My pieces changed color from orange to a couple different shades of brown but are now completely sealed and water beads right off. They have no noticeable smell. This might not be perfect for decorated pieces but worked very well for what I intended.

In Slavic area, we had a tradition of sealing / tempering with żur, zhur soup, made of lactofermented rye. Is it any known in the US?

maybe it's good to mention that people should put the pot into a COLD oven to start with and then let them both heat up. Loved seeing this, Andy. And if you were making a mug with the milk seal, there wouldn't be any residue left after because you drink your tea or coffee faster.

Good change in the audio quality. Rewatched it for the sake of the algorithm... The denaturation of the milk proteins reminds me of casein based paints :)

If it's the protein in the milk, then you should try a sealing with milk based protein shake/supplement powder.

Thank you for this and all your videos. May I suggest in when evaluating a seal in future you try weighing your pots before and after filling to show how much is soaking into the pot?

Hi there Andy, interesting channel! About sealing and milk sealing in particular. I do some reenactment and historical crafts. In my opinion pottery have historically been sealed in different ways according to what the purpose the vessel will have. What it is suppose to keep. For drinking water I would use beeswax or any combo with beeswax. seed oil I think needs to oxidize, wish take longer time, as when you make an oil cloth. then one will hang it in the sun to dry and "harden" for weeks... I got a tip from another history geek who is a potter about milk sealing for keeping oil... She told me to let is soak in milk and keep the "residue" layer after emptying it. Then just set it aside and let it sour for a long time. (like months) then it should be fine. I haven't tested this yet myself. Keep up the good work

I've read from some potters that you can just use yogurt or a slurry to coat the pot as an alternative to soaking. Additionally, some say just putting several coats on the surface is enough to make a seal.. Since you're not trying to "glue" a cracked item. Additonally, it seems like the reason the dairy works is due to the caisen protein.

The use of milk immediately makes me think of galalith. It was the go to plastic before the development of petroleum based plastic. It was used to make things like buttons. It's very simple to make at home with just milk and vinegar. The commercially produced galalith was soaked in formaldehyde which made it extra hard. But the homemade stuff is still plenty strong. I think I'll try experimenting!

To make a water-resistant paint I combine casein with quicklime putty (aged at least 70 month). It's been uses for millenia to make adhesive and binders. Ones quicklime dries it turns into limestone again.

I wonder if this is the same as milk paint and sealant. The casein protein is coagulated from the milk with an acid then reacted with a base turns it into a glue that is watered down and pigments are added to make paint. Plain milk, preferably skim milk, can be sprayed onto things as a sealant for artwork/wall paint and it is waterproof/resistant as long as the protein layer remains intact. Some people say there is a sour smell as these products dry but that it goes away after some time. The one time I used milk paint I didn't notice a smell. Idk about heating this up. I wonder also if eggs (which would be expensive but if you had a bunch of them from your chickens and they were going bad, you might as well use them) could be used. Egg yolks are also used as paint and are waterproof/resistant once dry but I doubt you could heat this up since proteins denature with heat.

It may be a year, but I believe that instead of "soaking it" maybe how about submerging it in milk? It's not my area of expertise however I believe it's the perfect way of truly saturating the vessel. Excellent work by the way, for some reason I'm hooked on your channel. Don't know if it's your voice, your train of thought, your chillness or just how good you are at making pottery but I really love your videos. Keep up the good work.

This is really educative! In Tibetan earthenware milk sealing is done just after the firing, while the pots are still hot, you can check out the video if you look for "Fire and Earth - The Tibetan Blackware Pottery". By the way, I tried firing black ware inside two barbecue lids put together into the fire so that the pots are practically sealed from the smoke except for two small holes were the handles were, and covered it up with sand once the fire was at its best. The pots came out all black although here there was arguably no smudging, so I suppose there is a deal of reduction and smudging if you only cover the pots with sand. Also it is important that the fire burns on while you have covered it by sand, and that the wood doesn't fall down. Perhaps reduction and smudging come generally hand in hand unless you can isolate the pots from the fire as I did with the double barbecue-lid. If you try out the barbecue lids be carefull to put a little sand into the one under the pots or the black paint of the barbecue might stick to the pots as it did happened to me. Balint

You say it is the proteins in the milk that causes the seal. That makes me think it might be the casin doing the work, which would make sense because that is also used as a glue in making musical instruments and bookbinding.

Thanks so much for your videos. Love how professional and super informative they are! ❤️

The Milk Seal Diet. I like it!

Thanks Andy, funny very interesting as usual!

The fats will convert over to a secondary polymer from the milk fat similar to cast iron sesoning sealing. It's why you dont wanna burn it since that will destroy any plastic type polymers created. I'd strongly reccomend using a more controlled method of heating to do this sealing to help convert everything and drive of the agents that can sour since that smell is typically caused by bacteria we can determine your milk soured during the process at some point.

Just a thought. If its the protein that binds with the clay, would gelatin dissolved in water be a good substitute for milk? You wouldn't have to worry about souring.

I know it isn't traditional, and have no idea if anyone has tried it before but if it is just the protein doing the sealing then what about using unflavored gelatin? I would try making a batch of knox flavorless gelatin and while it is still hot put it in the pot, and perhaps keep it warm next to a fire, or even on the fire to keep it at a simmer while it is soaking to keep the gelatin liquid. Dump out the gelatin and let the pot cool down, then rinse off the inside and out with cold water and light scrubbing before firing it like you did for the milk.

Hi Andy. My father and I have just started making pottery and your videos have been a wonderful source of information for us. We were wondering if you have ever considered sealing pottery with the oil from jojoba seeds?

Have you experimented with firing up to 600 or 660? I've seen a few tutorials mention going to those temperatures for milk glaze and they don't seem to have the issue of milk to scrub off. I'm not sure if it would still be sealed, but maybe it would lose the bad odor...

U can weight water before and after for better accuracy.

If it really is protein that seals it Peas belnded with water could be a great sub for vegan. I will have to try that

Why do you consistently use macro scale measuring? Switch to milliliters and you will have a much better idea of volume loss. Additionally cover or seal the lid and you will eliminate evaporative loss. This combined will give you a far more accurate indication of volume loss through the walls of the vessel.

Any chance you have articles or books that talk about where milk sealing took place? Or any historical data? Thanks!

I have two lovely matt glazed earthenware oil lamps that I discovered to my horror leaked the lamp oil I filled them with. So I thought I would try this method for sealing them. Still not sure if the soaking in milk will do or should I bake them afterwards? And how long to soak?

It sounds like what you're doing is sealing the pores in the vessel with casein (a polymer found in milk that can be turned into a crude plastic.) there might be other ways to do it by directly applying casein curds to the pores of the vessel. Of course. that's literally what all the other primitive methods do as well, use a polymer to plug the hole

Dude you are the best, can you tell me how much I need for your class?

Hi Andy, if this problem of sealing pottery existed up until the last 1000 - 300 years, depending on where in the world you were, how did ancient people store things like beer/wine, where the liquid has to stay in the vessel for weeks/months? Thanks, Callum

Thanks for your video, do you sell any of your clay so I can't make crafts with my daughter? Thanks.

I see. Back to the oil lamp video.

Have you tried sealing with pine resin? I would love to see the results of that.

Milk sealed pottery diet. Awesome…. also keeps your hand out of the cookie jar !!

I've got my best results with olive oil.

Had this been bisque fired prior to soaking?

What is melk?

Haha

I thought you boil the milk inside thepot?

a milk sealed pottery diet plan Huh!?? funny

the protein you are talking about is casein! fun fact, in a similar process to making cheese, you can extract the casein and make cups and bowls and plates, and the best part is, if you throw it outside, it'll biodegrade in just 30 days! which is why i think it'd be a WONDERFUL alternative to Styrofoam plates, of course if you get a press to press the casein! and it'd reduce SOOOO much Styrofoam waste!