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Best way to dry earthenware platter

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Do you throw platters...?

Tuesday 12 Sept

I've just thrown a charger/platter/big flat bowl using about 6lb of white earthenware, total diameter 14"  includes a 2" rim all around flat base prob 1" thick will be turned, removing  1lb+ of clay to give a shallow foot (prob with an inner and central foot for extra support in kiln).  This will be a decorative display piece so weight does not matter, in fact in this instance the heavier the better really.  It's been ribbed so nice smooth finish and I've wired through the base with a twisted cut off wire.  It's sitting on the throwing bat which is marine ply, I wasn't intending to move it off that until it is leather hard+. Current atmosphere is a shaded room,  cool room temperature. I don't normally make these, but I need to decorate it at leather hard stage and fire it  for a gallery exhibition that will be setting up in 2 weeks' time

My question: what's best way of drying this so that it doesn't crack through rushing it, but still have it ready to decorate, preferably in a week's time?

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My routine for drying platters is to throw on day 1, in the morning preferably then leave them alone until the end of the day then covered loosely with plastic overnight. I use plaster batts now but have used wood ones in the past. For wiring off pots with a thick base using a heavy cutoff wire seemed to work better than a thin one, I would wire off right after throwing the pots.  (no wiring off with plaster batts needed)

Day 2 I put a foam batt on the platter, it’s just big enough to fit on the flat inner surface, not the rim, and I flip the platters over. Upholstery foam is glued onto a batt so it’s rigid underneath but soft on the inside so it doesn't get dinged up. Upside down platter goes on a support (like a bunch of other odd batts) so the rim doesn’t get messed up by hitting a shelf, and left alone for the rest of the day. During day 2 the plaster will pop off the platters, I remove it and leave the upside platter alone for the rest of the day and loosely cover with plastic overnight. You don't want the walls to dry out much more than the base, I like getting the batts off and platters upside down as soon as possible.

Day 3 I trim then leave the platters right side up and cover the rims only with long wide strips of plastic, basically just leaving the middle of the platter exposed. In my climate they take about a week to fully dry after trimming.  

I would suggest making the base and wall thickness as even as possible, having too thick a base can cause drying cracks from uneven shrinkage and/or dunting. Heavy and robust is fine, just keep all the areas as even as possible.

Edited by Min
Tyler Miller and oly like this

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41 minutes ago, Min said:

My routine for drying platters is to throw on day 1, in the morning preferably then leave them alone until the end of the day then covered loosely with plastic overnight. I use plaster batts now but have used wood ones in the past. For wiring off pots with a thick base using a heavy cutoff wire seemed to work better than a thin one, I would wire off right after throwing the pots.  (no wiring off with plaster batts needed)

Day 2 I put a foam batt on the platter, it’s just big enough to fit on the flat inner surface, not the rim, and I flip the platters over. Upholstery foam is glued onto a batt so it’s rigid underneath but soft on the inside so it doesn't get dinged up. Upside down platter goes on a support (like a bunch of other odd batts) so the rim doesn’t get messed up by hitting a shelf, and left alone for the rest of the day. During day 2 the plaster will pop off the platters, I remove it and leave the upside platter alone for the rest of the day and loosely cover with plastic overnight. You don't want the walls to dry out much more than the base, I like getting the batts off and platters upside down as soon as possible.

Day 3 I trim then leave the platters right side up and cover the rims only with long wide strips of plastic, basically just leaving the middle of the platter exposed. In my climate they take about a week to fully dry after trimming.  

I would suggest making the base and wall thickness as even as possible, having too thick a base can cause drying cracks from uneven shrinkage and/or dunting. Heavy and robust is fine, just keep all the areas as even as possible.

Min – that is brilliant so glad now I asked! My wife has found an old flat cushion with a piece of foam that could be perfect I will build it up a little as necessary. I wonder do you trim base with it just resting on the foam/wood bat or do you also add a larger bat so rim edge is supported somewhat? 

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No support under the rim. Just attach the foam covered batt in your usual manner to the wheelhead. If it touches the wheelhead just build up a chum (tall flat topped cone of clay) and stick your foam batt to that. My platters are too large to fit inside my splashpan so I remove it and put a large piece of plastic  film on the floor to the right of the wheel where the trimmings fly off. I bundle up the trimmings in the plastic when done and dump them in the reclaim. Best of luck!

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3 hours ago, Min said:

No support under the rim. Just attach the foam covered batt in your usual manner to the wheelhead. If it touches the wheelhead just build up a chum (tall flat topped cone of clay) and stick your foam batt to that. My platters are too large to fit inside my splashpan so I remove it and put a large piece of plastic  film on the floor to the right of the wheel where the trimmings fly off. I bundle up the trimmings in the plastic when done and dump them in the reclaim. Best of luck!

I guess by the time the platter gets to the wheel it must be okay to adjust its position on the foam to get it 'perfectly' centred for trimming?  The clay should be firm enough to take a little mild adjustment by lifting and moving it a bit?  I'd have to lift it by its rim, perhaps with help of some foam-covered lengths of batten to spread load?

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Nope, I really wouldn't lift it by the rim.  I don't use batt pins so am able to just give the foam topped batt the platter is on a nudge to get it centered. Do you use batt pins? If you do then I would put a thick ring or pancake of clay on your wheel, deep enough to cover the pins then place your batt on that. You would be able to nudge it into center then.

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8 hours ago, Min said:

Nope, I really wouldn't lift it by the rim.  I don't use batt pins so am able to just give the foam topped batt the platter is on a nudge to get it centered. Do you use batt pins? If you do then I would put a thick ring or pancake of clay on your wheel, deep enough to cover the pins then place your batt on that. You would be able to nudge it into center then.

Min, thanks so much this information gives me the best chance of getting this right first time which would be wonderful.  I do use bat pins now but no problem, I will do as you suggest and set the bat on clay. Brilliant! :) 

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Update - all good so far, platter is off bat, trimmed and drying with rim covered! Base is thinner than I wanted (should have used more clay) but fingers crossed it's on its way :) I followed Min's instructions work perfectly :)

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