Repairing crack in unevenly dried greenware

[Ginny C]

Thought this piece was carefully covered but one section dried out too fast and cracked. Can i get the whole piece back to damp enough to repair? Lots of time and  my last bit of colored clay went into this piece! B Mix cone 5 clay. Even slab. 
should i wrap in damp cloth and plastic and wait for it to bemoe evenly damp? Then fill the hopefully narrower crack with paper clay? 

[Bill Kielb]

I have never had luck repairing these especially successfully through the glaze firing. The only way I know I can rehydrate for sure is under pressure and steam. You might get a damp box to get you there but in my experience pretty hard to do with routine success especially with that crack that extends through the rim and that shape. Just my experience though, someone might have a fail safe method.

I am not a super fan of paper clay though as I find it’s usually less dense when fully fired. So often good in intermediate tests and intermediate workability but not so much for me after fully fired.

Only anecdotal experience btw where  I knocked off many handles from bisqued and finished mugs, probably more than 20 each to find the strongest join for my handles.

[Ginny C]

Thank you for replying so thoroughly, Bill.  What a lesson for me! Sigh.  
Does anyone out there have a success story? 
if i can at least get it damp enough to cut off the rim and make it into a much smaller plate, I would feel  better. So I wil keep trying. 
Later update: the wet dish towel (thin flour sack material) certainly has overnight softened the clay and apparently evened it out pretty well! But I stupidly left it right side up, so the sides slumped as they softened, making the crack even worse!! Now it is upside down on a round pillow, withe damp cloths on both sides. I was able to gently push the crack together and will do that several more times today. 
now it is a nice challenge! 

[JohnnyK]

This may ultimately turn out to be an experiment for you, Ginny...losing the piece in the end, but what you might do is take some of the trimmings from the plate and mix it into a paste with white vinegar. Then groove the crack (and maybe drill a small hole at the inside end of the crack to keep it from travelling further). Swipe some vinegar into the crack and hole and brush or press the paste into the crack with a slight buildup so you can sand the buildup smooth later, then cover the piece with plastic and slow dry it. This process is one we used in school and had good outcomes most of the time.

[neilestrick]

Cracks coming down from the rim are very difficult to repair. I don't usually recommend even trying, but at this point you've got nothing to lose. Vinegar slip or paper clay are your best bets.

In my experience, rim cracks usually occur if the rim is flexed when the piece is too dry, or it's left sitting on a hump mold too long, not from drying too quickly or unevenly.

[Babs]

Alao looks like your comoured vlay cube is closer to edge of plate...slightly different ratwe of shrinkage or indeedshrinkage beteen rhe coloured and non coloured can cause such cracking. 

Very slow drying with this sort of work.

I wouldn't use time trying to sort this.

[Chilly]

You could completely re-shape the rim.

As suggested above, drill a hole at the inside point of the crack.  Then drill holes in similar, but random, places all around the rest of the rim, say 5 or 7 holes.  Then cut waves into the rim, meeting each hole.

Obviously not what your first design was intended to be, but, hey, you might like it!

[Pres]

@Ginny CI am not trying to be unsupportive here, but just a few questions? How long did it take to make the piece? How long would it take to remake the piece? Are there any design improvements that the second piece could have that the first does not? Would you be able to dry the second piece well enough to prevent cracking? Now, the major question. . . .How much time are you willing to put into reviving the present piece? If the answer is less than 3 hours, then I would say to make a new piece. 3 hours may seem like an overestimate, but consider the spraying and wrapping, for several days; the repairing of the crack once reconstituted; the remake of the surface design as there will be ruined and smudged areas; and finally the effort to keep the piece from drying too quickly. One last item. . . . ..It may not work!

Sorry to sound discouraging, but it is all IMHO

 

best,

Pres

[Min]

When reading this thread the theme that comes across to me is not only about a long shot repair but the resiliency that's necessary to make pots. So many things that can go wrong with making pots...design, forming, drying, glazing, firing, lots of places to have screw ups.  I know it's a really hard thing to put so much work into a piece then have dismal results but it's part of making pots.  I was talking to a friend the other day about failures. When I went to school the general rule of thumb was to expect a 10% failure rate. I've got that figure way down since then but during those 30 years I've had entire kiln loads that were trash. It happens. Not getting attached to a pot until it comes out the glaze kiln successfully really helps. 

[Pres]

Just like Christmas, sometimes you get the gift you always wanted, and other time you get a funky tie!

Speaking of. . . . . . Merry Christmas !

 

 

best,

Pres

[Ginny C]

 Hi again. Ye I know that repairing is usually a waste of time! But since I do not sell my pots and do have lots of time, I got the piece all softened up and made 4 little plates.  FYI, old flour sack dish cloths wring out and wrapped closely on the piece, then plastic tightly brought it to soft leather hard in a couple of days.

 

[Bill Kielb]

Nice job!