Clays & Glazes

The ARTS Center – Ceramics Studio

GLAZING

BASIC STEPS

• Organize your bisque ware and decide on glaze techniques and combinations.
• Sketch / describe each pot briefly in glaze notes and record the glazes / techniques you used. That’s the only way to reproduce a glaze that turned out well. Trust us on this: you likely won’t remember.
• Wax bottoms of pots carefully so you don’t get drips where you don’t want them.
• Clean pots (wipe with a clean, well-wrung-out sponge).
• Dip, pour, or brush glazes.

USING GLAZES

• Mix glaze thoroughly before using!  Use the labeled brush in each bucket. Incomplete mixing will change the chemistry and performance of the glaze. Glaze ingredients do not settle out evenly. Stir from bottom to top as well as in a circular motion (like whisking eggs) to achieve an even consistency. Be sure there is no sludge left in the bottom of the bucket and no thin watery layer at the top.
• Mix again frequently. Glaze begins to settle as soon as you stop mixing.
• Each mixing brush stays in its assigned glaze bucket. Do not rinse brushes or leave them out of their buckets any longer than necessary. Do not contaminate brushes by placing them where other glazes can spill on them.
• Do not add or remove water from any glaze bucket. Report any consistency problems (too thick? too thin?) If it seems wrong to you, tell the monitor – don’t alter it or just use it!
• Do not contaminate glazes. Even small amounts of one glaze added to another can change results. Skim off and discard glaze that gets into the wrong bucket or on its lid.
• Set glaze-pouring cups down on newspaper – not on the bucket lids. Dried glaze under lids creates lumps when it falls into the bucket.
• If using brush-on wax on your pot as a decorating technique, be sure wax is dry before dipping. Wet or damp wax will trap glaze instead of repelling it. When the wax melts off during the firing, the glaze will still be there.
• If brushing on glaze, mix glaze thoroughly, then take a small amount out in a cup for brushing. It will be easier to keep the glaze mixed for use. Return any unused portion to the glaze bucket. Be SURE you know which bucket it came from; some glazes look similar.
• Do not apply glaze to the bottom of the pot or between lids and rims. Glaze melts into liquid glass, which hardens on cooling, fusing pots to shelves and lids to pots.
• Many glazes run more when combined than alone.  When combining glazes, allow room for that action. Be conservative with your application until you understand the glaze combination. Glaze that runs off of your pot onto the kiln shelf will ruin the bottom of your pot and may affect others’ pieces. It may also require that you pay for a new shelf (see related post in “Policies”). If you’re concerned that a glaze may run, put a note inside the pot requesting a “cookie” (a fired clay disk). Monitors will fire it with a “cookie” underneath it.
• Leave an unglazed margin of approximately one-quarter inch at the bottom edge of your pot. Almost all glazes have some tendency to flow.
• Do not dip pots too slowly. One to three seconds in the glaze (“one thousand,” “two thousand,” “three thousand”)  provides adequate coverage. Test tiles will indicate how long to dip a particular glaze.
• Glaze that cracks and peels away from the pot must be washed off.  If fired, it will continue to peel and fall off of your pot onto others around it. See the next note regarding multiple coats.
• If you are dipping a pot in more than one glaze, each coat must dry before you apply the next coat. Remember, multiple coats create thicker glaze application, so consider the combined thickness of glaze. The one- to three- second rule applies as combined time for all glaze applied. Each coat will take longer to dry because the previous coat has saturated the bisque ware’s porous surface.
• Freshly glazed surfaces are very fragile. Avoid handling pots before glaze has dried, and be mindful of the pressure you apply. Avoid holding a glazed pot by the glazed rim. Avoid crowding pots against each other.
• If you are dipping a pot in more than one glaze, clean the bottom of your pot before dipping in the second glaze. Note that multiple layers are more prone to damage from handling.
• Always clean the bottom of your pot with a damp sponge, even if it has been waxed. Dirty work will be rejected from the glaze kiln as will any work judged to be improperly glazed (glaze too thick, too close to bottom edge of pot, etc.)
• Leave the area where you glazed cleaner than you found it. Rinse all items except mixing brushes you used during glazing (tongs, sticks, cups, sponges, etc.) and damp-wipe all glaze from table tops.  Also, wipe spills from the floor with a floor sponge. This is a healthy studio issue!
• Be sure the glaze buckets are closed and the lids are flat on the tops of the buckets. Lids do not have to be snapped or screwed on, but they should not be propped up by the brush handle or left askew on the rim. REMEMBER, open bucket = evaporation = change in the performance of the glaze (not to mention bugs and dirt).

  

EXPERIMENT!

• Experiment with the positioning & application of the glaze and/or with using more than two glazes on a single piece, maintaining an acceptable total glaze thickness.  Some of these combinations can be beautiful.
• But the first time you use a new combination, please keep it on the inside or near the top of your piece until you see how far it runs, etc., to help save our kiln shelves and yourself the cost of a new shelf (and your lost work) and possibly others the headache of losing work when the glaze ran
• Keep good notes! Include info on techniques and order of application of your glazes. It’s frustrating to get a beautiful result and not know how it was achieved.
• If you want to glaze the inside and outside of a piece separately, be sure the bisque has time to dry before applying the second coat. If you are doing two coats in a combination that tends to run, be sure you dip the ware QUICKLY and avoid doubling all the way to the bottom edge on the outside. Whenever possible, do the doubling on the top half instead of toward the bottom on your form.
• For tape resist, apply tape directly to clean dry bisque — it won’t stick on top of a coat of glaze.
• For wax resist, apply wax over a bottom coat of glaze.
• Creating your own test tiles or test pots is encouraged!
• If your glazing will take place over several days instead of all at once, leave    notes with the pots on what needs to happen next.
• Remember that not all work must be glazed. The only surfaces that must be glazed are those that will come in contact with food/beverage. 
• Remember that color combinations do not produce logical, predictable results. Don’t assume! Glaze is about chemistry, not color mixing.
• Be willing to assess each result as it comes from the kiln. Being too set on a certain result can lead to disappointment. And again – be sure to note which glazes you used so that you can try to reproduce a pleasing result.

NOTES ABOUT OUR (UPCOMING) NEW GLAZES:

We’ll fill in specifics about the glazes that Cindy Hart is generously helping us with after they’re available. Stay tuned!

These notes were adapted from Nan Rothwell (www.nanrothwellpottery.com) who adapted them from Beth Turbeville (Peninsula Fine Arts Center). Both gave permission for us to further adapt this useful information for our own use.
Summer 2013