Top 7 Glazing Pottery Tips
... is the key. I know you are excited and want to get your pots in the kiln ASAP but try not to rush your glazing process. Glazing always takes me longer than I think it will. For my 95 litre kiln I give myself a full day.
Prepare your kiln
Save your expensive kiln shelves- use batt wash. If your shelves have lots of old wash on them, scrape it off and start again. Give your kiln a hoover out once in a while to get rid of particles and dust that might fall on your pots- I use a brush attachment on my hoover and brush the roof of the lid too- it’s surprising how much dust can collect in the crevices.
Rinse or sponge your bisque
I have clay and glaze I can get away with not rinsing/ or sponging but I also have clay and glaze combos which come out full of pin holes, craters and glaze bubbles if I don’t. In my opinion it’s always worth the effort.
If sanding your pots you should never skip this step- a quick blow won’t get rid of the dust (and you shouldn’t be blowing clay dust anyway!) Always wash pots which have sat in your studio for a while- they will have gathered a lot of dust.
After washing your pots leave enough time for them to dry out (ideally overnight) before glazing them otherwise the water in them will mean they won’t be as absorbent and your glaze will be too thin.
Use wax sparingly
It gives off horrid fumes. I only wax bases when I need to submerge an entire pot. I don’t wax pots where I am applying a brush on glaze. Wax each pot away from your main batch, not over the top of it- it can be so annoying to get a speck of wax where you don’t want it and the only real way to get rid of it is to bisque your pot again.
I know lots of Potters who don’t enjoy glazing but it’s a crucial step in the making process. A good pot can be completely ruined by bad glazing. Rushing through the glazing process rarely gets good results.
Personally, I quite enjoy it, mainly because I know the next time I see my pots they will be finished and I’m always excited by that Christmas morning kiln opening moment.
2. Testing, one, two...
Test your new glazes before putting them on a whole batch of work- sounds obvious I know but the impatient part of me always says ‘ oh it will be ok- I’m sure it will work fine...’ flip to 36 hours later and I’m looking at a muddy brown mess on that lovely little vase I was so proud of. So, trust me on the testing....
I make test tiles in a few different ways- one method is just cutting little rectangles of clay tiles- embossing in a pattern so I can see how the glaze reacts to texture. I scratch the name of the glaze into the back, add a hole in the top for hanging- these are great for brush on glazes.
Second method is I throw a large bowl shape on the wheel without a bottom, so I just have walls- fatter at the bottom and thinner at the top. I wait for the shape to get leather hard then using a wire I cut it off the wheel head and into sections like hours on a clock faceeach of the segments will be a test swatch.
Because they stand up on a little chubby bases these little flattened pawn shapes are great for testing dipping glazes or glazes with a tendency to run.
To brush, pour, dip or spray?
Each application method is suited to different shaped pots, the effect you’re trying to achieve and your level of skill and patience.
Pros: I find gives the most control (but then I was trained as a painter so maybe it’s just because I am comfortable with a brush in my hand) Great for detailed work.
Cons: it’s time consuming especially for larger pieces. It can be expensive if using commercial glazes.
Pros: it’s quick. It can give uniform results if done well. It’s cheaper than brush on glazes.
Cons: you need to be relatively confident in your mixing methods. Make sure your glaze is the correct thickness- too thin and it will look wishy-washy. Too thick and it could run. I use the finger test- dip your finger into the glazeif it coats your finger tip like single cream but you can still see the lines in your cuticle you’ve got it about right.
Pros: great for larger and difficult shaped pots. Can give great effects.
Cons: you need to have a big enough bucket to catch the pour off. Can be very messy. Can be tricky to pull off unless you’re confident.
Pros: very even application. Quick (once set up) Can give very interesting effects
Cons: you need a lot of gear. Spray booth, a glaze gun, a respirator.
Health and safety is much more of a consideration. In my experience you need a lot more room for spraying. Most potters who spray glaze have a permanent set up in their studio.
This might be a bit of a touchy subject for some. I hope it’s taken in the spirit it is meant... You’re not entitled to another potter’s glaze recipe.
Experienced potters have often spent years trying out glazes, testing clay/glaze combinations and tweaking recipes to find exactly the right aesthetic. Subsequently they’ll have 100s of failed pots to show for it. It’s absolutely fine to ask a potter about their glazes but don’t be offended if they don’t tell you the recipe, brand or even if it’s a commercial glaze or not.
If they do then you are very, very lucky. It’s a bit like asking a chef for their grand mother’s secret pasta sauce- it will probably die with them (Unless they write a book and can monetised their efforts).
It’s wonderful and very generous to share (if you want to) but we innovate by trying new things- find your own ‘secret sauce’ you can be proud of.
5. Heat work is different to temperature
When I first started Pottery nearly 13 years ago I couldn’t actually believe that cones were the only accurate way to measure the temperature a kiln reaches during a firingit just seemed a bit archaic in this time of technology. ‘You mean I have to risk singeing my eyebrows, peering through this tiny hole to see if that equally tiny piece of ceramic has bent?’ Turns out it’s as sophisticated as it gets in Pottery.
Cones have been formulated to melt and bend at very specific melting point within 5 degrees centigrade. A thermocouple or pyrometer can only measure the temperature of the air in your kiln, a cone will measure the amount of heat energy transferred into the ceramic material itself and that’s what you are interested in.
A sensor in a thermocouple will degrade over time with repeated cone 6 firings so cones really are the only way to check your temperatures are accurate and the health of your kiln. I rarely look into the depths of a white hot kiln now- it’s not worth the cataracts- but I do put cones in every firing and study them when they emerge.
6. Keep notes
This plate is one of my favourite things I ever made. The one that got away...the blue glaze on this plate is a gorgeous matt satin with delicate tans and greys peeping through subtle crystalsits one of the first things I made in my very own kiln, I didn’t take any notes. I have tried and failed to make it again, again and again- I’m still sad about that plate.
Now, I keep a little note book next to my kiln with all my firing notes. I write down: the date, what I’m firing e.g 30 mugs, Frosty Blue Green Glaze, the firing schedule and if I’m happy with the results. If I’m not quite familiar with with a glaze I might keep my cone stacks too- I write the date of the firing on the bottom so I can cross reference it with my notes later. A little kiln diary is also useful in terms of keeping track of the age of your elements.Keep good notes people!
7. Rectifying mistakes
Pin holes, crazing, shivering, craters etc... lot of mistakes which occur in the glaze of a pot can be to do with earlier stages in the process; under firing your bisque, not mixing glazes thoroughly, matching correct clay to glaze to ensure they ‘fit’ and proper house keeping in your studio and kiln.
Many problems can be rectified by slowing down your firing. This ensures work is vitrified, any trapped carbon can burn out and allows glazes to mature.
Careful though- because heat work increases with the length of a firing so it’s really important to keep track of your cones- you might need to drop the top temperature.
It’s best to under fire rather than over fire as you can re-fire under-fired work. You can’t do anything about an over fire tho apart from the bin! It is possible to reglaze a piece you aren’t happy with - in my experience the results can be hit and miss. But if you aren’t happy with the results of a first firing then what have you got to loose?