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How Much Grog to Wet Clay for Raku

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How much grog is best added to B-Mix for use in Raku.

Answer = what percentage, by weight, is an appropriate amount? 10%, 20%, 35%, 50%, ?????????


99% of Google hits are about adding amounts to raw materials to make a clay body. I put all the values I found into my black box and the result was 20% to the question above. I think 20% is too much but I don't know. I do know it took a heck of a lot of wedging to get a pound of grog into 5 pounds of clay and by appearance and wedging behavior it seems like its way too much.

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Sounds about right, depends on how quickly you are heating and cooling the pots etc. Fine or medium grog? If you guesstimate the wet clay having around 20% water you will be a bit over your 20% grog target but it should be close enough. Have you tried cut and slam wedging to get the grog mixed in? Video below if you need it. When I've added grog (or sand) to clay I make a rough block shape with the clay, slice it up and sprinkle the grog on each layer then slam them together. Add water with a spray bottle as you need. Once the grog is layered into the block then do the slice and slam wedging to get it mixed in. 


Edited by Min
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Thanks Min. Here's how I do it:

- roll out five pounds of clay

- spread a layer of grog (Kyanite 35 mesh)

- roll that up, slice and slam wedge

- repeat until all the grog has been added

- spiral wedge, then to the wheel


One thing that makes me think 20% (1lb grog to 5lb clay) is too much is B-Mix 5 with grog from the store doesn't' look at all like my B-Mix with 20% grog.

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I haven’t, even though I do have some. I just got started with Raku so wanted to do all my learning curve stuff with some reclaim I have which is a scrap mix of B-mix 5 w/wo grog, some Buncombe and other ‘whites’. There’s not a lot of b w/grog in it. So far what I’ve used without adding grog has done well with few cracks; only one explosion so far. :rolleyes:

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On 9/17/2021 at 4:11 PM, Min said:

I believe B-Mix with grog is going to be much finer than 35 mesh. I'm guessing it's more like an 80 mesh. 

I’m betting you are right. I tried to find out on Google but couldn’t find B-Mix specifications that went that deep. Searching Google for “what mesh grog for raku” the prime hit is 20 mesh. Couldn’t find that locally so went with 35. I’m going to cut back from 20%, my gut is telling me that’s just too much. Will try 10% and 35 mesh and see what happens.

Thanks for the responses Min!

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