Testing, Testing, 1,2,3...

Any potter will tell you that testing glazes sucks.
There is just no easy way to do it. It's time consuming and tedious, truly an evil necessity if one is looking for their own glazes that stand out in a crowd.

So I spent many hours this past week doing what I hate: testing glazes.

It has taken me many years to get to a point in glaze testing where I'm no longer rushing through it as fast as I can. I've made WAAAYYY too many mistakes doing just that. I've finally learned to slow down, clear my schedule for the afternoon, pull up a stool and get it done right.

So this time around I'm working on two different glaze bases: a glossy from the geniuses at Digitalfire, and a matte, a recipe that was given to me from the amazing and talented people at NSCAD. I will spend hours researching the colors that I am looking for: what ceramic oxides will yield what results, what ingredients are necessary in the base glaze to give the desired effect. I hunt down appropriate base recipes and calculate them using Insight, a downloadable glaze calculation program (highly recommend it!) and make sure all the numbers look good.

With all the research out of the way, I mix up 500g batches of each, with no colorants, and run each batch through a 120 mesh sieve. Then each glaze is weighed and divided into 5 different containers, all carefully marked with my trusty sharpie. It is at this point that the real test mixing begins. Colorants and stains are carefully measured into each well-labelled container (learned that the hard way, more than once!) and are then ready to be applied to test tiles.

I used to use lots of itsy-bitsy L-shaped tiles that I extruded. Each glazed surface was no more than 1" x 2". I have since moved on to larger surfaces. I found I just couldn't get enough information off of that small a surface. I need to actually SEE what the glaze is going to do, in the manner in which I'm going to be using it. Now I extrude tubes, about 3-4" tall, and 2 1/2" wide. This gives me lots of room to try as much as I need to on the same surface. Each tube is CAREFULLY labelled (also learned that the hard way, more than once!) and at the same time, I make very thorough notes in my sketchbook (again, the hard way...).

Glaze testing is painfully slow. After the research, there's the mixing. After the mixing, there's the firing. After the firing, you have to wait for the kiln to cool. After the kiln cools, you FINALLY get to look at the tiles, and inevitably, try to figure out what to adjust the next time around to get the results you are looking for. It can literally take weeks, months and even years to finally hit the jackpot and get what you were looking for in the first place. As frustrating as it is in the thick of it all, when you finally get that perfect glaze, all of that time spent doesn't seem so bad. It's like hitting pay dirt.

So for all of you out there who are also enduring glaze hell, hang in there! Without all the testing, you'll never find what you're looking for, and sooner or later your efforts will pay off.

More felt, more glaze tests, more frustrations...

Okay. So this has been a rather long and somewhat frustrating week. I managed to get a glaze firing in, along with some of those tests that I am working on. You'll recall from my last post, the problems I was having with my glaze running too much


I mixed up a couple more tests. Both tests are an altered version of the original matte glaze recipe, G1214Z from Digitalfire. I changed the glaze with my Insight Glaze Calculation Program to allow for a 5% increase in Silica. I thought I'd start with this alteration in my tests because it would help to stiffen the glaze and keep if from running, by slightly bumping up its firing temperature. I'm not very happy with the results. The tile on the left has no opacifier, the tile on the right does. You'll notice that I managed to correct the problem of the glaze running too much, but I think I prefer the matter surface of the original glaze recipe. So back to the testing... I think the next round, I'll work on the levels of EPK. If I increase the EPK and the silica at the same time, I may be able to both fix the running, and push the surface more matte. If I simply remove the extra silica and increase the alumina (EPK), then I'll make the glaze more matte than the original, which I don't think is what I want to do. I have to be careful adding too much more EPK, because that can cause the glaze to crawl. Here's an article about this glaze recipe, for further reading.

Back to my felting, I've started decorating some of the tiles I was working on last week:

The small piece on the right is a test piece I tried. The red stripe was wet-felted in place. This creates a very soft and fuzzy line. For the tile on the left, the red lines were added by needle felting. The two colours of wool do not blend the same and the red is much crisper. Personally, I'm leaning towards the look on the right. So I guess I'm testing more of this as well. (I see lots of testing in my future...)

I found some craftspeople online who are willing to answer my questions about felting so now I've got some brains to pick. The RagingWool has offered to help me (I know! Great name!) and so has LaLaFelt who has some amazing roving in stock!

So I'm off for another week of testing: glazes and felting. Enjoy!

Feltware

I've been hard at work trying a bunch of new glaze recipes for a line of work I'm going to call 'Feltware'.

After trying several cone 6 matte glaze recipes, I've decided to narrow it down to this one that I got off of the Digitalfire website


I'm loving the glaze. It mixes well and goes on very easily. It also has great colour response. I'm currently looking for a dark, slate gray. My first tests gave me this:

The surface is incredible! There is so much depth to the color, it's fantastic! HOWEVER, see those runs? The next few tests made a mess of my kiln shelf. NOT GOOD.

Soooooooo, a few more tests:

The first picture, confusingly marked '2', is the above mentioned glaze recipe with twice the colorants as the original test piece. I was hoping that if the glaze was darker, I could apply it thinner and get the effect I was looking for. Aparently, I was wrong. (surprise, surprise!) The glaze has a distinctly green tinge to it. The second picture is that original recipe, from the first test above. I wanted to see if I could repeat the results. The answer is sort of. Oh boy. More testing in my future...

As you can see, I still have the problem of the running, and in defense of the glaze, I AM overfiring it by about a cone.

Soooo, back to the testing. I can increase the alumina in the glaze to help with the running but that will also make the glaze more matte, which is not what I want. If I want to keep the current matteness then I could increase the silica along with the alumina which would also raise the firing temp a bit, which would probably help me out anyways, so that's most likely the route I'll go.

As for the feltware, it's coming.
I'm really enjoying felting. I've been working on a series of tiles:

This roving I bought at Romni Wools in Toronto.

This particular colour, eggplant, came in a bag with red and black roving. I LOVE this color. And ordered more along with some complimentary colors from A Childs Dream

These tiles will look very different by the time I'm done with them. I'll just have to be patient and check the mail.