Monday, 28 February 2011

Cardew inspired large jar.

This is the large Cardew inspired jar I made, with the four handles.  The handles are too big - way too big - but I like it all the same.  It is a very good weight too (ie quite light for me) and it wasn't turned.  The glaze is the new honey glaze, which has come out slightly darker and flatter than the test tile.  It went on really thick.

The oxides - iron, manganese and some cobalt - are quite rough as they weren't sieved, just blown from the hand, as it came out of the packet.  Not sure about that, but then it isn't a functional pot really.

I also like the neck as the throwing lines stand out just enough under the thick glaze and slip.

Inevitably, though, the rim has peeled really badly, so, can't sell this one either.

Friday, 25 February 2011

Test tiles tell us it's all Tosh.

Well, the test tiles are out of the kiln.  I wanted to make sure that the firing was just like any other, so i changed nothing.  The only difference being that I left the kiln a bit longer before opening it.  To pack out the kiln, I filled it with some beakers and a bowl using the glaze with the china clay in it.

One would hope that, under these conditions, the fault we're trying to fix would occur on the packing pots.  But it hasn't.  In fact, no sign of any peeling on any of the pots.

Anyway, here are the test tiles.  A few nice ones, and a few duffers.  The main duffer was 70% LBS, 30% hyplas, which was opaque.  A good start.

I put some cones in the kiln.  I had modified the firing slightly, a few weeks ago, and it is clear that I am now only getting cone 03, with cone 02 half down.  Well, that's ok.

My favourite of the tests was the one I was most trying to avoid - the standard honey glaze, 75% LBS 25% body clay.  The second tile has the black slip on it.  It isn't black with the glaze on it - it's a dark brown - but the slip is black where the glaze isn't on it.  Which is good, because I was going to draw through the glaze, a la Cardew.

The next two - 5 (80% LBS 20% AT) and 6 (90% LBS 10% AT) are pretty good.  I prefer number 6, but not sure that 90% LBS is a good idea.

The next two are honey glazes of a sort, but quite light.  One is 80% LBS 10% red clay 10% nepheline, and the other is 60% LBS 10% borax frit 15% red clay 15% hyplas.  They're both quite nice but they're a bit streaky.

Here's the packing pots.  Not that nice.

Look at this beaker - this is the china clay recipe.  It's gone cloudy.  Quite surprised by that and not entirely sure why.  Well, it doesn't matter anyway, because it's getting thrown away, when I can work out where I'm going to throw it.

Well, not sure I've really solved anything, but I am going to mix some of (1) and either (5) or (6).

I've been looking at Dorothy Kemp's odd slipware book.  She doesn't mention shelling at all, and says that the glaze pings off if you open the kiln too early.  She also suggests a recipe for borax frit, which is just a mix of the frit and body clay.  I might try that, just to see what it's like.  I have some test tiles left.

Tuesday, 22 February 2011

More wrongness.

So, I did a new batch of glaze yesterday, hoping that it would fix the peeling issue.  I know that, to fix the peeling, you need to reduce the amount of silica in the glaze - it's the opposite of crazing - and so I used a china clay which is much lower in silica.  But I kept the proportions the same - 80% LBS, 20% clay (16% china clay, 4% hyplas, plus 1% bentonite.)  I raw glazed two pots that weren't that great, so I didn't really care what happened to them.  Here they are:

Well, the quality of the glaze is really nice.  It's very clear, slightly less yellow that the last one.  I specifically want that.

But it didn't stop the pinging off of the glaze.  I did - and this might not have helped - well, the kiln was quite hot when I opened it and removed the pot.  About 150 degrees.  But I think the peeling isn't necessarily to do with that - it's the glaze needs fixing.

So today I've made some test tiles.  I did this by making some small bowls - dog bowl type bowls - which I've quartered.  The reason for doing this is because I want the tiles to be like these rims - so they're shammy'ed and the outside is ribbed, just like these pots.  I've slipped them halfway across, so half is slipped and half is just plain clay.  I have 23 tiles (one has the black slip - I want to see what it's like.)

I'm going to do tests in proportions of LBS to various clays, in 70/30, 80/20 and 90/10 tests, using AT, ESVA and china clay.  I can't guarantee that this peeling is going to happen.  So I will do two of each - one for top shelf and one for at the bottom.  The ideal would be to find a glaze that crazes, so i can then add some silica to to fix the crazing.

I've also got some borax frit, but all the glazes call for colemanite (either as it is, or in fritted form) which I don't have.  Wondering whether to abandon lead, but almost every earthenware potter I know is using it and does produce nice glazes.  Why don't they get this problem?  (I'm even using their glazes!)

Just need these tiles to dry so I can bisque them, now.  Not doing any more glaze firings until I've done the tests, I think.

Monday, 21 February 2011

Start the week with a wrong 'un.

I've been quite keen to get one of these larger jars that i've been making through the whole process.  So to help this, I put a couple of them on a radiator on Friday, to see if I could speed up the drying process.  Well, one of the pair - my favourite of the two - just ended up cracking on the base, but the other appeared unaffected.  So I bisque fired it.

The result.  A small s-crack in the base.  That's ok, I thought, I'll just glaze the pot all over.  So I did.  And here it is, fresh from the kiln this morning.

To be honest I'm not that pleased with it.  I like the decoration, and I like the fact that the slip was very wet when I did it.  But the glaze has no depth.  In fact, I put the glaze on really thick and all you can see is thousands of tiny bubbles.  So much so that, where they are most prevalent - at the base - the glaze is almost opaque.

Add to this that the glaze has shelled from the rim

And the base looks like the surface of a distant planet, and it boils down to not being good.

I largely wanted one through the process so that I could take photos, for a couple of fairs I'm going to apply to.  But I'm not even sure it'll do for that.  So it's back to the drawing board.

I have mixed up some more glaze using a lower-silica clay.  In fact, the glaze is 5Kg LBS, 1Kg Grolleg, 125g Hyplas, 100g Bentonite.  I included the hyplas because it is the slip clay.  The grolleg has much less silica than the hyplas clay so should help the glaze fit.  I haven't tested it - it's a complete punt really - and will probably end in disaster.  But... other recipes I've seen use china clay quite a lot, so we'll see.  The main ingredient is still LBS by a long shot, so it might not make any difference.  I might need a higher proportion of clay.

There were a couple of other pots in the firing.  Although I'm not sure about the shape of this bowl anymore (I've got seven others to fire - they're more rice bowl than anything) I like the patterning.

And these two cups came out pretty ok.

Of course, given what I know about the glaze shelling, I'm not sure whether to risk selling these, as you never quite know when the shelling will happen (so far, it's always been when the pots have come out of the kiln.)  So I think I'm not firing anymore functional ware until I know it's fixed.

In fact, my next project is cheap and cheerful terracotta flower pots to sell on the side of the road.  Thinking I might grow some veg plants to sell too - I can usually do growth to seedling level - it's after that that i have trouble.

Friday, 18 February 2011

Doing stuff.

I've mixed up a new batch of white slip this morning.  I did a bit of slipping yesterday, but for these bigger pots, my bucket is too small, and the slip wasn't deep enough.  Anyway, here's the bellarmine, with handle, slipped.

I might make some more of these - it was a pot went wrong, actually, and half way through I decided it was going to be a bottle.  When I belly out, I belly out from the bottom first, but that shrinks the pot.  So I also belly out from the top down, which stretches the clay but keeps the height (I also pull-up and belly out at the same time, earlier on in the process.)  Anyway, it lost it a bit half way through, but I quite like it.  This may get scratched on by someone who's turning out to be quite good at it.

I have also slipped some beakers.  They're very Winchcombe:

I prefer the half-slipped ones I think.  This is what they turn out like:

When pots go wrong, they tend to go in to service in one of the family households.  Yesterday, I discovered that my pots tend to leak a bit - they sweat a bit underneath.  I started out glazing functional pots all over, and firing on stilts.  I'm wondering whether to go back to that.  Saying that, almost all the earthenware pots I have do exactly the same.  It doesn't worry me, I'm just a bit worried that it might worry the people who buy my pots.

These mixing bowls came out of the kiln yesterday:

These were inspired by day-time television.  I saw one being used - filled with stewed fruit, or some jam or something, in a Devon cottage.

Again, I quite like them, but they are very rough and ready.  What I call country pots - made and decorated quickly, I guess.  I'm trying to spend a bit more time on things and be a bit more careful.

Actually, they look better in real life.  The sun isn't out here, so the pictures look a bit drab.

Wednesday, 16 February 2011

An update.

It's been quite a nice day here, on and off.  The sun is shining as it sets over the Ouse cut-off channel.  The gate is shut.  My windscreen has been replaced after cracking even more over the weekend.

So I've been making some bigger pots.  Not sure where I can fire these yet, but I'll work that out.  I saw - or I thought I saw - a photo of some jars that Michael Cardew made, in one of the books I have.  Well, I can't find it and I don't think it exists, in fact.  So what inspired me last week to make these, I don't know:

They are more like the shape I made for those ash-covered jars I made for wood-firing, except these are earthenware.  I'm not sure what they're going to be like, or whether they're a bit old fashioned, but I shall fire them and see.  There was another one that got the slip trailer treatment, which didn't work, so I spread it out with my fingers and it'll be kind of Korean in style, if I fire it.

I have to admit that I cheat with these.   I make them with thick bases and then turn them on a chuck.  I can control the shape better then, although I don't like all these shapes (the last one, in particular, I'm not sure about.)

And today, I've made a couple more big jars, again, Cardew inspired.  But this time, they are thrown as-is - no thicker bases.  In fact, they're a bit of a Cardew rip-off really, except I can't make pots with nice throwing rings.  Here are the two I made:

I'm not sure about the one with the handles - the handles look too big, although the pot is a good 12 inches tall.  The other might get lugs or something.  I was thinking of either mixing up a black slip and then drawing through the glaze, or a white slip with blowing on an oxide - iron or manganese.

Also made two bottles:

The last one will get a little jug handle, probably.

These pots are all a bit rough and ready, but they're what I can make at the moment.  And although I made a load of beakers today as well, the small things only go so far, and I need to make things that'll give a bit more of a whack, even if it's only £40 (and I can fire it for that.)

Anyway, more to do tomorrow - bowls and mugs specifically.

Wednesday, 9 February 2011

Turning and slipping bowls.

Another little video - a bit shorter this time - showing me cutting a foot on a bowl, and then slipping and decorating it.  I'm not sure I like the bowls very much - they're more soupy than breakfasty I think, which since spring is on its way, is perhaps not what I should be making.  Who knows?

Also, I received this in the post today:

It's a slip trailer, made by my friend Hannah.  I shall try to put it to good use, although I doubt I'd ever be as good with it as she is.  Thanks H.

Friday, 4 February 2011

New pots, again.

Some new pots out of the kiln this morning.  Some are ok, some are not to my liking.  The brush work pots are an experiment - I like the ones with the broad brush marks, but not the cross or round-the-body leaf patterns - I like them on other peoples pots, i just can't do it.

I like the stripey pots - especially the two square sectioned footed cups.

Downside - some of these are showing signs of shivering - the glaze on the rims is coming off in sharp little bits of glass.  I think this is partly the temperature - possibly producing bubbles in the glaze - there's nothing much in the glaze to cause issues.  Will think about a solution at some point.  Only happens on the clear glaze, not on the yellow glaze, which is a shame as I was thinking of concentrating on the clear glaze.  We'll see.