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So, I am making these large bowls that have holes drilled in the bottom, inside the foot ring. The purpose is to drain liquid from fruit, salad, veggies etc. I have been using an electric drill to make said holes.

The problem is, that in the drying, because there are holes across the bottom, there is a weakness and some of them crack. No matter how slowly I dry these bowls, some of them crack.

Any thoughts, solutions?

TJR.

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Tom

I made colanders for decades though its been a few decades since I did some.

I used a cordless drill with mostly stoneware clays with no troubles. I always drilled out holes inside foot ring.

I stayed about at least 1/2 inch from one hole to another. I used a hole size of 3/16 to 1/4 inch depending on glazes as they add thickness. My guess is you are doing it to late in the drying process??What type of clay are you using?

any thoughts on how leather hard they are? I used to spin light lines while trimming to have a guide on holes and keep them so the pattern was offset.

The other thing is are they to thin?the wall thickness I mean?Colanders need to have some thickness to them as they get knocked around a bit.

I thought by now You and the family would be in the Caribbean for a few weeks to warm the bones?

We are in a extremely rainy time 0ver 15 inches so far this month alone .

Mark

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Never made a colander, but could the direction the drill bit is turning make a difference? Like, the rotation is putting too much torque on that one spot in the clay?

 

You might try drilling from the other side? (i.e. if you're currently going at it from the bottom, try drilling from the top)

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I don't do colanders but my 'shell' bowls have areas with holes. I cut them with hole cutters at the leather hard stage too. I've also experienced cracking between them, on occasions. I think it's the thinness of the remaining clay in these areas as opposed to the more solid, unpierced surrounding areas - different drying rates and tension. Whatever you can do to slow / equalise the drying rate could help. How about a small wad of cling film (think you call it something else over there - the thin, off-the-roll plastic sandwich/food wrap), rolled and put through each hole and the whole area covered in plastic, and the whole bowl loosely wrapped? My very fragile pieces with thin clay additions that also crack in the same way, I put into a damp box to even out for about a week, before removing and loosely wrapping the thinner parts as above.

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Tom

I made colanders for decades though its been a few decades since I did some.

I used a cordless drill with mostly stoneware clays with no troubles. I always drilled out holes inside foot ring.

I stayed about at least 1/2 inch from one hole to another. I used a hole size of 3/16 to 1/4 inch depending on glazes as they add thickness. My guess is you are doing it to late in the drying process??What type of clay are you using?

any thoughts on how leather hard they are? I used to spin light lines while trimming to have a guide on holes and keep them so the pattern was offset.

The other thing is are they to thin?the wall thickness I mean?Colanders need to have some thickness to them as they get knocked around a bit.

I thought by now You and the family would be in the Caribbean for a few weeks to warm the bones?

We are in a extremely rainy time 0ver 15 inches so far this month alone .

Mark

Mark;

I think you have some good suggestions here. I will try to cut the holes earlier in the drying. I am using Danish White stoneware clay from Laguna. Also using a cordless drill. Don't know what size drill bit at the moment.

We are not going anywhere at Christmas this year. Went to Cuba last year before those dang Americans invaded. I am planning on going to NCECA in March, but that's about it.

Tom.

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I am familiar with Danish white with and without grog

I just pugged up 250#s of each which I mix together 50/50 for an older potter friend who is 84 and cannot wedge much anymore

I do this every year for her.

That body should take those holes fine as its pretty forgiving.

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Are you trimming a foot ring at all, or just cutting it flat? The added compression from trimming might help.

Diesel;

I'm cutting a pattern inside a foot ring, using a cordless drill.

TJR.

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Tom,

 

Have you tried using a hole cutter like these?:

 

http://ecx.images-amazon.com/images/I/31BCmfE7JPL._SY355_.jpg

 

 

Definitely not as fast as a drill, but maybe it would put less stress on the clay, and prevent the cracking.

 

I do agree with Mark though as well.  Creating the holes, when the clay is more plastic will probably solve the problem.

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Tom,

 

Have you tried using a hole cutter like these?:

 

http://ecx.images-amazon.com/images/I/31BCmfE7JPL._SY355_.jpg

 

 

Definitely not as fast as a drill, but maybe it would put less stress on the clay, and prevent the cracking.

 

I do agree with Mark though as well.  Creating the holes, when the clay is more plastic will probably solve the problem.

Ben;

I've got a couple of those in the studio. It's worth the time for me if it's less stress on the pot.

I will try to make the holes earlier on as Mark suggests, and I'll try that hole maker.

Tom.

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I wonder if your drill bit isn't as perfect as they once made them. On the cheap set of bits I foolishly purchased, I see the tips wobble a tiny bit. This slight wobble would create more internal stresses than a perfectly true and sharp bit.

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I've tried several things successfully not yet mentioned.

 

1. In early leather hard, wax both sides of future perforations, and lay it on pretty heavily.

2. Use a "plastic" drill bit. The entry angle is very high (60 degrees or so), so shaves the hole instead of punching it.

3. For that matter, consider using two bits: one very small, and one larger to finish. Don't get too happy with the second, cause that's where all of the ruinous mistakes will happen. I usually think I'm done on the last hole and relax and botch it there.

4. Use a very high speed when drilling. Slower catches the sides.

5. Wax your bit in between holes, literally. Although the drilling will wipe this off it seems to help. Tried silicone but didn't seem to make any difference. Beeswax is nicest.

6. Finally, drill from the inside if you can. The punch-outs are less damaging from the inside aesthetically.

7. Although backing it with something (for strength) works with other materials, the meeting between the clay and the backer always seems to ruin the clay. Dunno know why, except maybe the difference in density might not work to the clays favor.

 

Ultimately, colanders/drainers are pet projects. So much time, the glazing isn't all that much fun either. Drill as few holes as you can get away with.

 

M

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