Tuesday, 26 March 2013

Post 85 More pots

Three posts in three days is not a rate that I can keep up but here are the shots of the three intermediate sized pots from the last firing with the shohins.

This one is moulded from my oval Wasen design, altered to have the squared flange and without the lower rib, to give a clean curved wall profile. It is 415  x 305 x  85. The light blue glaze has darker blue highlights and breaks to a greeny beige colour.


This next one is based on my Tarraibune design, shortened in every direction to finish up at 395 x  270 x 76. The glaze is one I first tested in July last year but not used before on a pot. It works really well and I will use it again for sure. The colour would be good for any deciduous tree and also white to offwhite flowering species; perfect for a gardenia for example where the flowers start white and then age to offwhite/gold.

This last one is a commissioned repeat of a previous make; the Tenmasen in 'slate' glaze. It is Pot No 35 while I'm now into the 60s and has been waiting in bisque inventory for the right moment. This robust design/glaze combination is one that always gets attention. Dimensions are 380 x 275 x 89.
I'm very happy with the stability of this pot. Making a dimensionally sound high fired rectangular pot is probably one of the more challenging tricks in this pottery game. On this last firing I tried something new to get better temperature distribution in the kiln, which seems to have been beneficial, but that's another story for another day.

Monday, 25 March 2013

Post 84 Big pots

At the other end of the scale from those little shohin pots are these couple of biggies the result of another commission push into somewhere I hadn't been before.

It's been an engaging challenge to design and build these two. Final finished length will be over 500mm for both of them which means they start in the raw clay state at 13% longer - which is getting close to 600mm. Larger size and heavier walls means more weight and one of the biggest adjustments has been with something as simple as turning them over - which is a two person job. Turning a wet clay pot is a risk at any size but avoiding shape deforming bumps and shocks at this scale is interesting.

They are still wrapped in plastic and still drying with a long way to go before finishing.

This one is a 'bowed wall rectangle', a very attractive design for a big pot.

And this one is a classic oval, designed for a massive swampie.

Sunday, 24 March 2013

Post 83 Glazed Shohins - new pots

It feels like a long time since I posted new pictures of recently glazed pots on the blog and it has been. All sorts of things have gotten in the way, starting in December with some termite remediation that seemed to go on forever and totally messed up my workshop space for the duration. Then a little trip away to absorb the colours and flavours of a different culture and here we are already, nearly at the end of March.

So it was good to fire up the kiln and get some of those little pots glazed. Here are the results. The first 6 pots range in length from 189 to 170, width 130 to 120 and height 45 to 51. The colours chosen are deliberately quite muted, pale blues, greens to offwhites with antique tinges.

 The last one this time was a smaller size about 163 x 119 x 52. The glaze for this one is a different base which is quite matte. The result has it looking like terracotta pot that has been overfired in a woodfired kiln, right on target.

There are another 4 all glazed up waiting for the next firing.
In this last firing I also had three intermediate sized ovals glazed and I'll post them soon.

Wednesday, 20 March 2013

Post 82 Shohin pots in the pipline

A couple of posts ago I talked about using polystyrene for  both press and slump moulds.

In my professional career I always find that accepting a challenge to deliver a result to a schedule is the most powerful catalyst to learning. When you take it on you may have only the haziest idea about how to execute the task, and at best an unattractive fallback plan. Necessity and innovation are great partners, in potting too.

I've been commissioned to make some pots recently, from 180mm to 550mm in length; circular, oval rectangular, square. While I have a few moulds for pots around the 300 to 400mm length nothing at either end of the spectrum and while I have made some hand/slab/coil constructed pots the result , both inside and outside the pot is not the same as with a mould. That does depend on the finish you are after and ok, I'm open to the thought that this might be a matter of capability and experience too!

And so this necessity lead me to experiment with polystyrene, as both mould and support while drying. Todays post is to show you a range of shohin pots that were the result of that experimentation. They have just had their bisque firing and I mixed the galzes for them today, for application tomorrow.
At this stage it is good just to absorb the variety of shapes without being distracted by colour.
The pots are not large, but the walls are quite fine and they take more time to complete than their size would suggest.

Which ones do you like the best, from 1 at the top to 10 at the bottom?




Tuesday, 19 March 2013

Post 81 Tanuki #3

With my two little taunki doing well and looking good I have been inspired to step up the scale a little. The picture of bleached white timber, red brown live vein and verdant green foliage in the juniper driftwood style is a very attractive one. But these trees are slow growers and take years to get to any size let alone make enought timber to expose some of it. Finding a redundant stump to carve into shape is problematic. Hence my ceramic tanuki - which will outlive any tree, daed or alive!

I've been cruising the net looking for exhibition shots and there are some great examples.

It always starts with a sketch. This is the sketch for my latest model.

Its always easy to put pencil to paper - the trick is to convincingly turn it into 3D.

So here is the still wet finished result - from the front. Its height is about 380mm and the channel for the tree is about 450mm in length.

From the RHS. The structure of old branches on this side of the tanuki is the 'oldest' part of the tree. As this part 'died back' the new 'S' shaped tree emerged to be the final support for the live vein. The old part has the appearance of being appended to and absorbed by the new.

This is a detailed shot of that RHS showing the avanced weathering it has suffered.

From the back you can see that I deviated from the sketch by keeping the same helical slope for the tree channel; it will be hard enough as it is to bend a tree into shape to fit. I've also made the channel taper from bottom to top too.

And this from the LHS. Now all I have to do is find a nice straight, flexible, single trunk shimpaku about 350 to 450 long.

Thursday, 14 March 2013

Post 80 My new best friend - Poly (styrene)

I'm always on the lookout for new and helpful ways for me to practise my craft. Recently a close relative had a crazy idea about making a replica amphora as a decorative object and was looking for a little workshop space; and tools; and help, to make it. 
He'd chosen polystyrene as the material of construction. It was a snap to make. From 100mm deep sheets we simply cut discs with predefined cut inclinations, to get close to the final overall profile. My little bandsaw cut it nice and cleanly and after gluing up the discs it was easily sanded to a pretty smooth surface. The cut surface accepts the normal range of water based fillers and acrylic paint. It will dissolve almost at the sight of any solvent based material.

So with a few scraps lying about what could I do but slap some clay on it and see how they behaved together; which wsa prett positive actually. The poly does take on board a little water but has nothing like the pulling power of plaser of paris, so if using it as a mould it is a matter of relying on air drying to firm it up and get that first releasing shrinkage.

Scraps lead on as they do to a separate order from the poly man. The material is cut with a hot wire and can be supplied in any size and thickness you might like to order. It is interesting to do a little search just to see how versatile the material is and how it is used and shaped for all sorts of applications.
As far as potterty use goes it's like any other mould material; the choices are basically press moulding (concave mould) or slump moulding (convex mould).

I've tried both. Here's a slump mould for a shohin pot - now second hand as you can see. Once you have a picture of what the inside of the pot will be like then you can follow any number of options for the shape and profile of the outside wall. With the slump mould you can apply sufficient pressure to the outside to get good shaping and surface uniformity. I didn't try to 'fill' the surface with spak filler but that's possible to get a smoother inner surface.

And then this is a press mould. The polystyrene when cut on the bandsaw and hand sanded lightly leaves a nice roughish surface. With the press mould you can work on the inside of the pot to get it right without worrying about distorting the pot. Getting the pot out of the mould isn't as easy as plaster but after a couple of days with a little drying out they pop.

Here's a pot out of the above press mould. Any little remnants of polystyrene on the clay will either fall off as it dries or get burnt off in the bisque firing.

Like all making processes, scaleup challenges abound and twice as big is much more than twice as hard. The next shot is of a scaled up poly mould. The real benefit of using this stuff is the weight. Turning a plaster mould this size is almost a trial of engineering where as with the polystyrene the weight of the clay is as good as all there is.

Why do this rather than handbuilding? Good question. I think if there is the prospect of making more than one to a certain size then the investment may be worth it. A mould also lets you work with wetter clay which I think gives you a better dimensional result. Handbuilding a pot which has more than just a little wall inclination and maintaining symmetry is not easy without crafted props anyway, and that is what the poly does. There are lots of choices to make in how to use this material to assist the process and I'll keep working at it for a while to see if I can crack it.

I've been working on some commissioned pots recently, a number of them quite large. The first batch are in the kiln for bisque firing today. There'll be a seies of new finished pots to see soon.

Saturday, 9 March 2013

Post 79 Brown glaze trials

My search for brown has continued with trial series 7 just fired. This was the first time I've experimented with chromium, having been reluctant to use it. So this was a matter of trying to find out just what I have been missing. As well as chasing browns I also ran a group of straight greens and also had a try at chrome reds (chrome and tin).

I used three base glazes in this trial. The first is my standard Post high calcium satin matte (test tile numbers under 7-42) the next is the Post tomato red base (tile numbers up to 7-48) and then just three using a high spodumene nutmeg  recipe. I lilke the tomato base as it produces very nice buttery surfaces with a slow cool-down cycle.

38 has a little Manganese in it which always give a standard brown colour whereas RIO will ore oftern than not give a slightly red tonality.  44 and 45 have only RIO and Yellow Ochre as colourants and set up side by side you can see the red tones coming out.

In this set there are a couple with some small amoubnt of chrome and zinc. I find the zinc invariably supercharges any iron colouration. If you can filter out a little of the reflectivity from a couple of these they are very similar. I really like 7-39 as a candidate to replicate the unglazed colouration frequently achieved in asian pots used with conifers.

The above two have heavy doses of both chrome and zinc - to bring zinc chromate as colourant into play and then RIO in 30 vs YO in 29. Once again the RIO gives more red tones and the YO more orange. Both of these offer good strong colours.

27 has a little cobalt as well as the RIO, zinc and chrome and has produced a little speckle and interesting bronzy tone which will be a very useful colour. Tile 40 againb shows the impact of a little manganese. It also has rutile but I think in this case has clouded the colour and it would bhave been better without it.

The last three are the nutmeg base tiles, with variations of RIO, YO and Tin Oxide. A wider testing of thes combinations would be useful. The colour of the darker red tones is pure rusty steel. 7-50 with just 2% iron and 3% tin is a great offwhite breakin red. In this one I mixed the RIO after sieving the glaze and so some larger particles produced nice spotting - a useful this to remember and one to put on a pot sometime.