A Tool For Line Blends / Currie Grids

[Pieter Mostert]

I hope to start working on some Currie grids soon, so have been thinking of ways of speeding up the process of mixing up the 35 glazes. I've designed a tool for making line blends (since Currie grids are just a series of line bends) but I'd like to get feedback on ways to improve it. What I'm aiming for is something that's significantly faster than measuring out volumes with a syringe or graduated cylinder, doesn't depend on the total volume of glaze (within limits), and is relatively cheap and easy to construct.

Here is roughly what the thing will look like.

The way it works is as follows. Suppose you want to make a line blend of glazes P and Q, with 5 mixtures. Tilt the tube to the right, and fill it part-way with glaze P.

(Sorry for the bad rendering). If the tube is on a level surface, the ratios of glaze in each section will be 1:2:3:4. Now roll the tube to the left, so that the glaze gets separated into 4 compartments.

Transfer the glazes into 5 containers (one of which doesn't get any glaze), then repeat the process with glaze Q, but reverse the order of the containers, so that you end up with mixtures of P and Q in proportions 0:4, 1:3, 2:2, 3:1, and 4:0.

One thing I'm undecided on is how best to transfer the glazes. You put a pouring lip on the left edge of each section, but this will make construction more complicated, and pouring off the largest compartment may be difficult since you need to get glaze spread over a large area to flow to a single point. You could put the pouring lips at the corners of the compartments, so that you can tilt the tube to direct the glaze towards the lips, but I'm not sure how well this will work.

Another option is to drill drainage holes in each compartment, cover them with sticky tape, and then uncover them one by one to drain each compartment. I have a feeling this could be messy though.

Or you could transfer the contents of three of the compartments using a syringe, and then just pour off the last compartment.

The design above is for making a line blend that results in 5 glazes, and it's clear how to modify it to increase the number. However, the trouble with doing so is that the greater the ratio of tube length to glaze-depth is, the harder it will be to maintain an even depth of glaze across the length of the tube, so unless you've got it perfectly level, you can expect the ratios of glaze in the different compartments to be off. So for the purposes of making a Currie grid, I'd probably make line blends from A to C and B to D the usual way, and then use the glaze separator on the 7 pairs of glazes corresponding to the ends of the rows.

As far as construction goes, I'm thinking of using a PVC pipe, into which I'll glue semi-circular plastic dividers. This could be a bit finicky, since you're dealing with relatively small dimensions. If you make up 500ml of each corner glaze in the Currie grid, you'll have about 57ml for each square, so the amount of glaze in the smallest compartment of the separator is one quarter of that, or about 14ml. Choosing the width of this compartment to be 20mm and choosing the inner radius of the pipe to be 25mm seem to be a good compromise between not having the compartment too narrow (hard to clean) and not having the tube length : glaze-depth ratio too high.

My only prior experience with constructing something out of plastic was making the rim for a small sieve by cutting a hole in a plastic lid with a scalpel I'd heated in a candle flame (there has to be a better way to do this...). So, I'd like recommendations on what plastic to use, how to cut it, what glue to use, how to avoid getting glue all over the place, etc. Or should I construct it out of something else?

Any ideas on how the design can be improved?
 

[High Bridge Pottery]

Could you make some little silicon plugs or something like that. I am thinking like the things on cheap water pistols that clip in and out to put water in. Maybe you could buy some of those. Couldn't find anything like that in a google search but there seems to be things out there to tap into a pvc pipe that you could seal or maybe it has a tap. http://www.rainbird.com/landscape/products/dripline/DriplineInsertAdapters.htm

 

Not sure how well it would work for the currie tiles but you could do the four sides like you say. I could see it working well for a line blend depending how much glaze it used. In my tests I like to hone them down so I use as little material and waste as possible.

 

The thing is this would not work with my methods, but if if fits in yours then I would try it. If I am blending a big mix of glazes I would currie tile it and I think a syringe is always going to be quickest, there is just time involved in making 35 glazes. When I am line blending it is normally adding one ingredient so I mix up a big batch of the base glaze to surface gravity 1.48 (I think, can't remember exact value) and call it 0.80g dry glaze per ml. If I take 50 ml that gives me 40g of glaze that I can add down to 0.25% (0.1g) pretty accurately and it at least gives me a blend that I can narrow down and possibly do a more accurate test. Most of the time they are good enough for me. Also lets you add lots of different materials to a glaze quite easy without continuously mixing glazes.

[sloan.quinn]

How common are 3D printers in SA? The county library here has one...I intend to see about using it to make stamps. That design seems like a prime candidate for 3D printing, if you can get access to a printer.

 

 

 

Another option is to drill drainage holes in each compartment, cover them with sticky tape, and then uncover them one by one to drain each compartment. I have a feeling this could be messy though.

 

I have a feeling it's going to be somewhat messy regardless of how you do it. What I'd do is rig up a cover (out of a piece of the next-size-up of PVC, perhaps) that slides out of the way, and then just have all my containers in place before you open up the cover. The key that way would be getting the closest fit you can to the outside of your pipe, so your compartments aren't just draining into the cover below.

 

I'm just tossing things at the wall to see what sticks, but that's my thoughts. Interesting project.

[Pieter Mostert]

High Bridge, a plug is better than my sticky-tape idea, but draining the glaze through the hole is still going to be messy. The dripline inserts wouldn't have this problem, but they protrude into the pipe, so you wouldn't be able to drain all the glaze.

You're right that this won't work well with small volumes - the surface tension of the glaze and variations in depth will have a greater effect the less glaze you use. When you do your line blends, do you add a colourant, dip a test-tile, add more colourant, dip a test-tile, etc?

I still feel this can speed up making Currie grids. Once you've made up 2 sides (not 4), you're left with pouring glazes into and out of the separator 14 times (twice for each row), whereas if you were doing it with a syringe, you'd have to measure 42 quantities of glaze (6 for each row).

I should also point out that you can use the design with 4 compartments to make line blends with 10 glazes. Split each end glaze into 3 containers with proportions 9:5:4 (either by using a syringe or a modified glaze separator), and mix two pairs to give you the mixtures in the line blend with ratios 4:5 and 5:4. Then make a line blend of the 0:9 and 4:5 mixtures, and a line blend of the 5:4 and 9:0 mixtures using the glaze separator. It might not be that much faster than doing it by hand, but if you're doing many line blends, the time you save could make it worthwhile.

Sloan.quinn, there's a maker space nearby that has a 3D printer, and I've thought about that, but I'd prefer a more low-tech solution, if possible. If I do go the 3D printing route, I should be able to solve the problem of pouring off the glaze (though designing a good lip may be a challenge), but I imagine the roughness of the printed product would make it hard to clean.

I hadn't thought of using an outer cover. It'll be faster than having plugs if the fit is right and there's no friction, but I suspect this will be hard to achieve.

[sloan.quinn]

I hadn't thought of using an outer cover. It'll be faster than having plugs if the fit is right and there's no friction, but I suspect this will be hard to achieve.

 

Shouldn't be too hard, really. If you can't get anything else to work, get PVC couplings that fit your pipe - the outside diameter of your pipe will match the inside diameter of the coupling. Cut the coupling in half, across the diameter - you may need to grind down the ridge that goes around the center on the inside (the bit that's there to stop you pushing the coupling too far onto one side of your joint.) That piece should fit your PVC like a glove. Rig up a set of slides with some epoxy and whatever material seems like it would work. If you have too much friction, well, a Dremel with a sanding pad can be your best friend sometimes. Just DON'T forget a dust mask and eye protection anytime you're making PVC dust fly around. That stuff is nasty.

 

Another option: get the next size up from your main PVC size, cut out your cover piece, then fix on a piece of firm foam (something like this, cut to fit) to make up for the diameter difference. Rig with slides as above. Doing it this way would let you slide it lengthwise, if you prefer, though you'd probably have to be prepared to replace the foam fairly regularly, since I don't think that stuff cleans all that well. It is fairly cheap, though, per square inch.

 

Hell, if none of that works, you could probably figure out a hinge/latch system. It would be messier, for sure, but you wouldn't have to worry about friction.

 

I just have mental images of trying to take out an oil plug (in a car) without threads when you talk about plugging the hole. And I've never managed to open one of those salt shakers with a plug without getting salt everywhere.

[bciskepottery]

A variation could be along the lines of the gadgets for weekly medicine doses where each compartment has a snap lid. Then you could just pour the glaze out and not bother with holes, plugs, etc.

[curt]

Hmmm...I like the idea of automating the Currie procedure but the mental image that keeps coming to mind is one of those medical labs where they are testing or modifying 100 samples at a time on a large tray in rapid succession. Kind of robotic...

 

I am not in love with the idea of moving a large quantity of glaze material around in a long open container over my 35 plastic cups. Seems risky...

 

I am thinking of a stationary, gravity-feed system with the 4 corner containers at the top, each hooked up to small tubes coming out the bottom which eventually lead into some kind of dosing apparatus (maybe like your long tray, maybe different) before leading down to 5 cups. Underneath is a movable tray with 35 plastic cups secured to it (or maybe those cups sit in purpose built cup holder so in the tray) with that tray moving systematically forward so that each row is dosed properly. I shift of a lever doses 5 cups at a time. Then move the tray forward and go again.

 

The tray with 35 cups could then be shifted to a table which acted like a paint can shaker you see in the hardware store, constantly agitating the glaze in each cups so ingredients didn't settle out.

 

I still think the dosing of finished glaze on to the test tiles would need to be done with a syringe, but that is because I am pretty particular about how that is done as I think how you apply the glaze in the cells has a massive impact on what you see when it comes out of the kiln and by extension your understanding and interpretation of the results.

 

The whole Currie process is pretty manual and as a result error prone as many of us know. However, it gives such powerful results that it is worth putting up with that. IF it can be automated that would help,a lot so this is definitely worth thinking about. Perhaps my sketchy ideas here will help the brainstorming process a little.

[High Bridge Pottery]

I think I slightly remembered that wrong. For doing a colour line blend I take out just over 70 ml twice so I can mix the two glazes and have enough ml to do the mixing. I actually do them on currie tiles going across and do multiples on one tile.

[Pieter Mostert]

Sloan.quinn, I'm probably misunderstanding you, but it sounds like you're suggesting the main tube sits inside 4 sections of half-pipe (joined with horizontal supports) that cover holes in the bottom, so that when you slide the bottom section to one side, the holes will be open. After thinking about the various options a bit more, I've decided that 1st prize would be a design without moving parts, so something that lets you pour out the contents of the compartments without making a big mess. I think this will also be the most time efficient. I have some ideas that I'll post once I've updated my CAD design.

Thanks for the warning about PVC dust. I didn't realise it was so bad.

Bruce, I'm unfamiliar with the gadgets you mention, so I'm not sure I understand your suggestion about snap lids. In any case, wouldn't it be hard to find lids that are the right proportions?

Curt, I would separate each row of cups from the others when pouring in the glaze. If you pour in the two end glazes from opposite sides, you won't have to rearrange the order.

If simplicity of design and construction weren't a consideration, you could design a system that's almost completely automated. If you have a device like a printers tray where the compartments are connected by small tubes, you could use this to subdivide each corner glaze into the proportions needed for the 35 glazes. Of course, you'd need a way of opening and closing the connecting tubes to level and then separate the glaze, and ideally this would be done by flipping a switch. If you arrange a tray of 35 cups under this device, you could drain the compartments directly into the cups using tubes attached to holes in the bottom (which you'd also need to open / close). Then it's just a matter of subdividing glaze A, rotating the tray of cups 180 degrees, subdividing glaze D, reversing the order of the columns, subdividing glaze C, rotating by 180 degrees, and subdividing glaze B. But all this is much too complicated for me.
 

High Bridge, I guess you use about half the volume of glaze for your line blends than what's usually used for each square in the Currie grid, so like you say, my device probably won't work that well.

[High Bridge Pottery]

Yea I ended up halfing all the numbers he uses in the grid

[High Bridge Pottery]

Yea I ended up halfing all the numbers he uses in the grid

[Pieter Mostert]

OK, here's my improved version.

I've attached a rectangular strip along what used to be the pouring edge, extended the partitions, and inserted wooden blocks to direct the glaze towards the openings through which it'll be poured out. I'm not sure how well this will pour, but it's better than my original version, even if it looks clunkier.

[bciskepottery]

Bruce, I'm unfamiliar with the gadgets you mention, so I'm not sure I understand your suggestion about snap lids. In any case, wouldn't it be hard to find lids that are the right proportions?