"Dry Footing" What Is It? And Why Won't Alice Shut Up About It?
Dry footing is the technical term for making sure that the bottom of your pottery does not have any glaze on it. Glaze gets sticky like glue when it goes into the hot hot hot fires of the kiln. As it goes through a chemical reaction in the heat it changes into its final state - which is essentially a thin layer of glass - which means that any part of your pottery that has glaze on it that touches the kiln shelf when it is loaded into the kiln will stick to it. Not only is this likely to ruin your piece of pottery but it can also damage my kiln shelves :-(
TOP TIP: Because of it's sticky nature you can actually use glaze as a glue if something falls off a piece of your pottery. Ask Alice about this in person.
Below are pictures before Dry footing - Notice how the green glaze has spilled over the edges and onto the base and how there are tiny bits of green in the centre.
To get rid of the bits we don’t want the most frequently used method is to use a soggy sponge. You can either hold your pot in your hand and use your other hand to wipe the excess glaze off. Or sometimes I like to use a big sponge, pop it on the table and wipe my piece of pottery across it a few times, applying a bit of pressure as I go. This way I know I’m not wiping any extra off accidentally. Just make sure that you don’t have your sponge too soggy for this - I would say medium soggy - and use an old sponge because often the texture of the pottery will rip the sponge up a little bit. Behold below the post wipe pottery butts - can you see how lovely and clean they look? No green at all!
Some blank bisque shapes come with a built in ‘foot’ for you to wipe, like the plate below, other potters may even make items with a foot for this reason. It’s a way that you can glaze the majority of the bottom of an item without having it stick to the kiln shelf. Essentially the rest of the base of the pot is elevated by this little foot. Have a look at some of the pottery in your house and see if you can notice it. You should find it on most manufactured ceramics as well on some handmade pots. It also has another function too, to prevent your pots from sliding around on the table. The raw pottery creates friction on the tables surface which will prevent it from flying right off the edge if it is knocked accidentally.
Anyway, the reason why I make such a big deal about people making sure they have wiped the butts of their pottery properly is because it can do real damage to the kiln shelves. I hate charging people for repairs so I would rather just nag you loads about making sure you double check.
I get lots of pottery through the studio each month especially seen as I do my own classes as well as take commissions. So sadly I don’t have time to check all of the bases! Each kiln might have maybe 150 - 500 pieces in it (especially if someone has made small pieces of jewellery) - it’s a lot of butts to wipe.
How to get around Dry Footing:
With Earthenware clays you can glaze your butts, but it means you will have to use a firing stilt - like the one above. It is made of a specialised concrete with metal pins set into it. The three points allow you to balance your item on the three points - meaning that the glaze can’t stick to the shelf.
They come in lots of different sizes and shapes, and you can also get ones that are made without metal and have ceramic points. My TOP TIP: is to AVOID AVOID AVOID this type. They are so easy to break and the points often get stuck onto your pottery creating a bit of a mess. With the metal ones you will have three contact points where the pins have touched your ceramic which are unavoidable but can also be sanded down so that you can't really see them. Another thing I would say is just to be really careful when you remove the stands from your pottery, tiny pieces of glass can get stuck onto the pins and it is very easy to cut yourself when removing a piece of pottery. I've done it myself before many times and ruined the ends of my fingertips, so learn from my mistakes and make sure that your fingers are well clear of the points when you try to pull the stand away from your pot. It's often actually safer to knock them off using the side of the table instead.
Unlike with Earthenware, because of the high temperatures the kiln will go to, the stilts can’t be used when firing to stoneware temperatures. The metal will warp when it gets too hot and so pieces can fall over etc. Because of this all Stoneware pieces need to have some sort of area that has been dry footed to go into the kiln.
A couple of other things to think about :
Some glazes might look pretty much the same colour as the clay when they have dried out. Because I didn’t make your pottery myself it can be hard for me to tell which is the bottom or top of your piece. I could accidentally put it the wrong way up in the kiln without realising, it has happened before, so its best to make sure you pack your items with the top facing upwards.
Also remember that I won’t fire any newspaper or organic matter like bits of plants or flowers that have been pressed into the clay. So make sure you remove anything like that before firing too ;-).