Slip Base by Susan Feagin question

[KB3d]

I would like to mix the slip recipe by Susan Feagin in Ceramic Recipies. 

Susan writes:”For batching: I weigh out the ingredients and make a 5000-gram dry-mix batch. When I’m ready to make colors, I measure out a 500-gram portion of the dry mix into a container, measure out dry Mason stains, and add that to the dry-mix slip base. Then I add water, mix, and sieve to make the slip smooth and perfect for brushing.” 

I am wondering, how would I mix the 5000-grams of dry ingredients thoroughly enough to use small portions, without creating airborne chemicals?

Thanks,

Karen Borg

[Callie Beller Diesel]

If you’re wanting to mix a large master batch that then gets divided out, leave out the dry mixing entirely, but weigh the water. If you know how much water went into the batch you can divide it out evenly. If you keep to metric measurements, this will be easier, because 1 ml of water weighs 1 gram. It doesn’t work like that for all fluids, but it does for water. If you are used to using a measuring cup, check how accurate it is by filling it to a given measurement line and weighing it to make sure it’s close enough for your purposes.

For instance, if you add 2500 g of water to your 5000g batch, the whole thing will weight 7500g, so a quantity of slip that weighs 1500g will contain 1000g of slip base. (Numbers made up off the top of my head for ease. You may have to play with your water additions to get your consistency right. Just record what you did.)

From there, you can add your colourants to portions of your master batch. To mix thoroughly, you will need to use a stick blender that rotates really fast. If you use something slower like a jiffy mixer, you’ll have to let it mix a lot longer to get everything distributed properly. For some colourants that don’t break up easily, you may have to sieve the mix again. 

[Min]

Another option would be to put the full 5kg batch into a pail with a lid that can be sealed on (twist type pail lid) then roll it and flip it around for 15 minutes or so. Leave the pail sit for a day for all the dust inside to settle then scoop it out just like any other dry material. If it sits for a while then roll it around again before using. I do smaller 500 gram test batches of base glazes like this all the time using a large freezer ziplock bag.

[High Bridge Pottery]

@Callie Beller Diesel You could write it out as:

dry weight = portion weight / total weight x batch weight

 

You could either work it out per bucket of slip or make sure to take the dry weight off the batch weight for next time you work it out. Using Callie's example ~

1500 / 7500 x 5000 = 1000 

if you wanted to keep working it out every time you need to take off the 1000 of dry weight from the batch weight for next time so it would be

1500 / 6000 x 4000 = 1000 (assuming you haven't lost water to evaporation) 

 

If the slip is thin enough to measure the volume accurately you can weigh a volume of slip and then

(volume of slip weight - same volume of water weight) x 5/3 = dry weight

 

If you can measure the specific gravity and know what dry weight you need you can also work out what volume of slip you want with

volume needed = (3 x dry weight) / ((5 x specific gravity) -5)

 

Edited April 4, 2023 by High Bridge Pottery

[KB3d]

Thanks Min.  

And thanks Calle and High Bridge