Tag Archives: electric kiln

Layering Glazes at JoVic Pottery

 

I once heard an elderly potter say “if I don’t like what I’m getting, I just fire it again.” That was not easy before potters began to fire pottery in electric kilns. In fact, those extra firings often resulted in pots for the yard, if not the garbage can.

Disappointing Glaze #1
Disappointing Twisted Sister # 1 at Mature Temperature

Firing pottery at Cone 6 in an electric kiln (in oxidation) wasn’t exciting in the past either. Potters often frowned upon the results, and those with gas or wood-fired kilns which make use of oxygen reduction to bring out the beauty of their glazes swore they would never switch to oxidation. You just could not get a lot of great color development unless you were using commercial glazes–or so it was believed. How could you get that great variation in glazes on your pots if you didn’t have the magic of the reduction fired atmosphere which helped add variety and depth and interest on just a single pot?

Refired Twisted Sister # 1
Delightful Result with Re-Fired Vase 1 “Twisted Sister”

But potters love to invent, whether it’s a new tool for their use in the studio, or a new glaze to put on their beloved pots. It seems much of the fun comes from experimenting. While there are still lots of potters quickly dipping their ware in buckets of glaze (and it’s admittedly much less expensive with so little waste), many of us are also using spray booths. This requires a good safe space to work with phenomenal ventilation. It also results in lots of waste of glaze chemicals. The upside, however, is that it enables a very even coating of glaze without the dreaded unintended drips marring the final surface finish.

Not that drips aren’t sometimes desired. But for a potter to be truly happy or excited, those drips need to be placed in such a way as to enhance the work. And since we’re firing in oxidation, and we’re spraying the glazes, well then why not look for ways to enhance color and texture by spraying different glazes onto a pot.

Bad Glaze Vase 2
Disappointing Vase #2 at Mature Temperature

Yes, there’s a lot of experimenting, and not just a few disappointments to contend with along the way. Each glaze causes reactions within the heat of that kiln, and some of those reactions aren’t just to the heat, but to the different glazes introduced.

Twisted Sister # 2 Beauty
Gorgeous Re-Fired Twisted Sister # 2

But back to the original statement, about firing again; it is now not just to salvage failure, we re-fire with intent. We increase the number of firings in order to bring about results we could not otherwise have with the typical bisque followed by one glaze fire. We don’t just add the exciting variety that potters formerly achieved with gas or wood-fired kilns: we have taken that to brand new heights. We don’t have to spray a pot evenly with just one color, we can use bits here and there, spraying gently, choosing a heavier application here and lighter one there.

After our initial bisque firing, we fire glazed pots at lower temperatures to ensure that the glazes adhere or you might say that they are baked on, usually at cone 04 somewhere in the neighborhood of 1900 ° F. Sometimes we add more glazes and again fire at that low temperature before finally firing our pots to maturity (or to a stoneware state)  at Cone 6, approximately 2200 ° F.  Some pots may have 3, 4, or even 5 firings before we decide they’re finished and ready to sell.

For a final finish, some of our pots are treated to a crawl glaze application, and this, too, is comical when we think about the former “taboo” of having a glaze crawl on our pottery.

Bisque Fire Glaze Load
Loading a Low Temp Fire in Electric Kiln

With electric oxidation firing, we can play to our heart’s content. We can introduce and generally control the crawl so that it enhances our work. And that’s true for our ash glaze applications as well. Ash glazes tend to run, but instead of worrying about the runs, we carefully introduce them just where we know they are likely to bring about some incredible beauty. The pots that in ages past relied on wood ash to create their glazes, well, I guess we’ve experimented and found ways of using them in an electric oxidation atmosphere.

Crawl Glazed Urn
Crawl Glaze Control on Beautiful Lidded Vessel

And just like that elderly potter, we’re happy to believe that we can even re-fire a pot that had previously reached stoneware maturity.

Wine Entertainment Set

JoVic Pottery’s Latest Kiln Delights

This last kiln load had us both smiling with glee. There are some gorgeous functional pieces, like the wine bricks and the tall stemmed goblets with crawl glaze decoration that take function to art and are absolutely perfect for entertaining special guests.

Crystalline & Layered Ash Glaze Bricks
Wine Bricks, Utensil Holders, or Vases–so functional, so decorative

Crystalline layered glazes with final ash glaze layers (Mt. St. Helen’s Ash actually), and fabulous tenmoku liner glazes on the interior which make the wine bricks not only functional, but allow them to become decorative vases or utensil holders.

Lidded Vessel with Ash Glazes
A beautiful Ginger Jar or Urn in Spring Shades $250.

And how delightful are large ginger jars with beautiful lids?

Urn with lid off
Lids are fired separately so that the rim of the pot is glazed too.

Should you want to use this beautiful jar as a vase, you might enjoy setting the lovely lid slightly to the front and side to give it an extra wow appearance.

Mt. St. Helen's Ash Lidded Pot
lidded pot with slip-combed decoration and layered glazes $125.

Also fresh from the kiln are two lovely lidded pots, again glazed with Mt. St. Helen’s ash layered over crystalline glazes. The similarity of these pieces comes from the skill of glaze applications–but slight tweaking of the process ensures that though the pots are alike, they remain unique.

Ash Glazed Lidded Jar
perhaps a perfect tea canister… $125.

Note the wonderful slip application–a treatment put onto the pots when they’re just slightly stiffened. Combing through the slip adds texture to the shoulders of the pots and also aids the “breaking” of glazes showing up color beneath the layers.

Vase in Blue and Green
Slip-Combed & Ash Glazed in Blues and Greens $125.

And the last vase here is a delight to hold and would be wonderful displayed with or without flowers. It, too, shows the benefit of slip-combed decoration which adds depth and texture. Engobes and crystalline glazes, sprayed over a period of several days to allow sufficient drying between applications adds so much visually and texturally. Come visit our studio in Ladysmith, BC on Vancouver Island to enjoy not only looking at, but touching and collecting work that brings art to function and function to art.

 

The Joy and Disappointments Unloading Kilns

Opening Kiln, top shelf
First sight on opening looks good

Anticipation is always exciting for us here at JoVic Pottery, however, it’s also a little bit nerve-wracking. How will things turn out in this firing? We do our very best to continue to develop glazes, always pushing limits. We also continue to use those glazes we think of as tested, tried, and true, especially some of the layered glazes we so love.

Spherical Vessel
Ash and Crystalline Glazed Vessel

No matter how often we use some of these glazes, the results are never fully guaranteed. Electric kiln firings are more easily controlled now than ever before in the history of pottery, and the variety of glaze approaches available in mid-range oxidation makes the process truly exciting. We use computer controlled kilns, giving us the ability to carefully control the firing time and even some of the time we allow kilns to “soak” at a specific temperature.

Stacked kiln shelves
Stacked shelves invite a peek

But even with such controls, the firings have a way of leading to both disappointment and joy. Some pots come out of the final glaze fire giving us just what we were hoping for, some exceed those hopes, and yet others appear with unexpected flaws.

Alligator Ginger Jar with Rim Spatter
Slight rim contamination on an otherwise perfect lidded pot

The kiln furniture attests to some of the surprises thrown our way (and I do mean thrown, pitched, or perhaps spit). We find evidence on shelves that suddenly require grinding because crawl glaze spitting occurred during the firing and the bits of glaze hitting shelves has fused onto them.

glaze spit on kiln shelf
Kiln shelf with glaze spatter

We’re even more disappointed when the spitting affects nearby pottery–turning a winner into a second and affecting the bottom line when it comes to earning a living from our work. This is an added risk when we’re using layer upon layer of glaze and adding crawl glaze texture for a final firing. In other words, we’ve already spent tons of time getting the pots to this final firing, and have put in the energy, literally as well as physically, into as many as 2 or 3 previous firings.

butter dish
Note the little fired in blotch on a butter dish base

We’re experienced. We’ve been at this work for over 35 years. But that doesn’t matter in the least when it comes to the occasional failures in the final product. We get to load beautiful pieces into our kiln, knowing the quality of our work is truly awesome, but sometimes we still end up unloading a pot that just hasn’t made it to the level we’re seeking.

Unloading Lovely Pot
Vic and Ash Glazed Lidded Pot

Whether some spitting hits an interior or the beautiful rim on the base of a pot, it’s still disappointing. It’s just a good thing that the majority of what we pull from the kiln makes us feel blessed to continue our work. We’re thrilled to say there’s always something to strive toward; because as long as there is a goal ahead, we’ll want to keep working, and for potters who won’t likely ever earn a great retirement package, that’s a really good thing.

 

Pottery-A Slow Process

Jan 2015 wheel throwing
Vic at the wheel

The making of quality stoneware pottery, whether functional or decorative, is far from a rapid process. Aside from clay preparation, pots made require careful drying before they can even be put through their first bisque fire.  But just the making is a time consuming thing, especially for large vases that are thrown in two stages.

Two-Piece Altered Vase by Vic Duffhues
Careful finishing of joined, altered vase by Vic Duffhues

Getting the neck onto the base requires careful joining; after all, if the pot is not put together correctly, the neck would come free of the vase. Careful smoothing and finishing is needed.

Potter's Wheel with Vic
Inspired Creativity

Then there’s a process that allows us to get some color onto the pieces before a first firing–of course not until the pieces are bone dry. We often spray the work with engobes, or brush on slip.

Kiln Load with Bisque-Glazed Pots
A Bisqued Load of Partially Glazed Pots

Once the pottery is again bone dry, we’re able to place the work into the kiln for a first firing. We bring them up slowly and cool slowly as well to avoid any potential cracking or warping through this cycle.

JoVic Partially Glazed & Fired Vases
Some Vases With Initial Fired-On Glazes

The cooled pots then need waxing before we can glaze. If we didn’t wax the bottoms the pottery would end up stuck to the kiln shelves.

JoVic Wax Station
Hot Wax Set-up with Exhaust

Once the waxing is finished, we can get on with the work of glazing. This is frequently a slow process because we tend to use multiple glazes and each coat must be completely dry before we add a next layer. Bisqued pottery is still somewhat porous, and the water base of the glazes is absorbed into the work, requiring careful and total drying between each step.

Waxed Mug
Hot Waxed Base

Some of our pottery is actually put through a few low temperature firings. This ensures that the first layers of glaze are fired on, allowing us to handle the pottery without smudging or accidentally removing some of the glazes. Though the glazes in this case have not reached a mature melt, they are stable enough to handle.

Bisque-Glazed Platter and Lidded Vessels
Kiln with Bisque-Glazed Platter and Lidded Vessels to Unload

Fired on glazes really help with some of our more complicated glaze applications. Crawl glazes, for instance, cannot be applied to glazes unless they have already been fired on at a lower temperature. By their very nature, as reticulating glazes, they would pull up any immature glazes they were placed on and instead of an attractive crawl, exposing lovely sub-surface colors or glazes, they’d end up exposing some terrible peeling effect that exposed clay.

Crawl Glaze Drying on Stoneware Platter
Glaze Drying in Bowl of Platter with Waxed-Over Glaze Rim

Each kiln load has us looking forward to seeing whether what we envision at the start of making our work actually lives up to our hopes.

Vic glazing Vase
Preparing to Glaze a Vase

With the glazes applied, the final drying begins.

Glazed Vases Ready to Fire
Glazed and Drying in advance of Firing

Once we’re sure the pots are dry, we can carefully load the kiln. Great care must be taken with vertical vases that have crawl glazes applied near the base.

Kiln loading at JoVic Pottery
Stacking the kiln for a final glaze firing

A slight bump and the glaze will fall off the pot, potentially leaving bare spots where they might not be desired, and also fusing to expensive kiln shelves or other kiln furniture.

Cone 6 Firing Ready to go
A Nicely Loaded Kiln Ready to Fire

Some of the final results pleased Jo Duffhues immensely–not so Vic. He’ll likely take the vases he’s not thrilled with and apply additional glazes for yet another re-fire.

Stoneware Vase
Vic’s not happy with this?

I have to remind him that some of our customers love the pieces that he is not excited about at all. The trouble is that when we work we have an idea of the outcome we’re seeking, and if things don’t turn out that way, we tend to think it’s a failure. It’s very hard to get past that kind of negative response. But since I love these pieces, I think they’re a great success.

Stoneware Vase Feb 2015
Multi-Glazed Stoneware Vase

Yes, these are the vases that Vic is seen making in the images above. Now it’s just a question of who wins the argument–will they be fired once again?