Thursday, January 19, 2017

January 15th Hint of the Week



 When to use Magic Water? (From Lakeside Pottery in Stamford, CT)


Magic water is used when the bond between two pieces of clay is a suspect for cracking during drying or bisque firing. Cracks can occur in the following conditions:
  1. When one piece of clay dries faster than the other which typically occurs when it has a smaller mass or thinner than the other piece (e.g., a mug handle).
  2. When one clay piece is applied to another piece that is already a dryer leather-hard (e.g., when waiting is required for a thrown pot to harden before applying hand-built piece).
The above two conditions are more susceptible to cracking because when one piece is dryer that the other, it is therefore shrunk more than the other and will not continue to shrink uniformly after they are attached to each other, thus - creating stress.

Consequently magic water is great for mixing with your clay to make “magic” slip to attach all your handles, spouts, sprigs, etc. It really works better than just plain water in your slip mix. So Magic Slip could be your go to slip for all attachments.

Magic Mud? Magic mud is the same as your slip, magic water and clay, but it is thicker almost like toothpaste. Magic mud can be used for more extreme cases. It enables the joining process to be less critical and therefore one can build more spontaneously as well as build wet clay on dryer clay. You can fill in stress cracks during drying and additional stress cracks will be reduced dramatically. It can also be used to connect broken bone-dry pots / sculptures. Sometimes it works fixing broken bisqued pots (needs to be re-bisqued after applying magic mud). When fixing broken bone-dry or bisqued pot, always apply more magic mud / magic slip than needed and build the layers slowly allowing the layers to dry in between applications. The excess slip can be filed down after the bisque firing.

Why does Magic Water work?
Sodium in the soda ash and the sodium silicate is a very powerful flux. The silica in the sodium silicate adds some glass-former. The water is to dissolve the soda ash (which is soluble) and therefore travels a little way into the wet clay. The sodium silicate is sticky and dries really hard and faster than the clay does. The end result is that the Magic Water makes a sticky layer of almost-glaze that soaks into the surrounding clay and dries hard. Thus, cracks are prevented in the drying and the bond is stronger after firing.

We keep a couple of milk jugs of magic water made up and on the shelf in the ∆10 glaze area. Bring a small container and take what you need for mixing in your slip. It is cheap and easy to make and we try to keep the magic water jugs full.

Thursday, January 12, 2017

Hint of the Week for January 8th



  Some Glazing & Decorating Stuff from Pottery-Magic.com.


·         Before you begin glazing always be sure to wipe your ceramic piece down with a damp sponge. This will make sure that there is no dust on your piece which could cause the glaze to pull away and leave a bare spot. Dampening helps the bisque to accept the glaze.
·         If you are painting on glaze, you must paint on three flowing coats of glaze, being careful of brushstrokes which could show up in unleaded glazes or if you use less than 3 coats. Three coats of glaze will give you a solid color. Adding another glaze for the second and/or third coat will give you some interesting effects. Let each coat dry before adding a second.
Best to brush in opposite direction
·         To show textured surfaces better, brush glaze on so it gets in all the cracks, then wipe off the top surface.
·         To remove oxide mistakes or for making a design, use a pencil eraser. It won't smear like trying to wash the oxide off.
·         When applying oxide over dry glaze, the glaze sucks the water out of your brush making it difficult to paint clean lines. To remedy this, lightly mist the glaze first with water and the oxide will flow smoothly.
·         When glazing a thin piece, glaze the inside then wait for it to dry thoroughly before glazing the outside. Otherwise the clay will become saturated and your piece will either fall apart because it will have absorbed so much water or the glaze won't absorb and stick to the outside. Sometimes it is best to at least let it dry overnight before glazing the outside.
o   [This is a common occurrence, for instance, when you glaze the inside of a cup with one glaze and the outside of a cup with another glaze].

Tuesday, December 27, 2016

The Last Hint of the Week...for the year


Underglaze From BigCeramicStore.com Tip #67
Confused by underglazes, that confusion may be caused by the fact that underglazes have changed throughout the years. [We have a few underglazes with the low fire glazes, but they are almost all for low fire, as the cone 6 & cone 10 glazes have been heavily used up this past year].

The original underglazes were quite similar to colored slips, made by adding pigments such as stains to watered down clay. Underglazes tend to be highly pigmented for strong color. They are desired for painting by many ceramists because they stay where you put them. In other words, the lines won't "flow" into each other like many glazes.

The original underglazes fire very dry or matt, so they were and are most often covered with a clear glaze [or a translucent glaze]. The underglazes are usually applied to wet clay or greenware. This way the "clay based" colors can shrink with the piece they are on and the glaze is more stable after bisquing and with subsequent firings with regular glazes.

In recent years glaze manufacturers have begun to make underglazes which can be applied to bisque. They do this by adding a more frit than clay. Frit contains silica which is one of the main ingredients in glaze. The silica causes the underglaze to "melt", effectively making it a little more like a glaze. This change allows you to apply the underglaze to bisque and/or to both greenware or bisque.

A few of these underglazes have enough "melt" that they are somewhat shiny and don't require a clear glaze. But you can put a clear glaze on any of them.

The next most common question involves when to apply the clear glaze (if you are applying one over the top of the underglaze.) If you are using underglaze on greenware, the most common method is to bisque the decorated greenware, then apply the clear glaze and fire again. One advantage of this is that you get a final chance to add more color/underglaze if you have an area that did not get enough coverage. Sometimes this problem doesn't show up until after a firing. Another advantage is that you won't risk messing up your design when you apply the clear glaze.

However, you can apply the clear glaze right over the top of the underglaze without a firing between. This is best done if you applied your underglaze to bisque, because greenware can absorb glaze and crack. There is also a risk that you can mess up the design by applying the clear. So a good approach is to sponge on the first coat of clear to help protect the underglaze. Then you can gently brush on your remaining coats. Often dipping the piece into clear glaze will not affect the underlying design either, but you should test as some underglazes do "dissolve" or "smudge" easier than others when a glaze is applied to it. Some clear glazes smudge the darker underglazes especially if the underglaze is not “bisqued-on” first.

Unlike glazes, underglaze colors can always be mixed together to create new colors. Also unlike glazes, the color when fired is similar to the color when wet (another reason why painters often prefer underglazes.)

However, a final consideration with underglazes has to do with firing temperatures. Technically all underglazes could go to the highest temperatures (such as Cone 10), but not all do. Although most Amaco Velvet series, all of the Coyote underglazes and a few others will go to cone 10, most others underglazes are fired lower [Always read the label carefully]. Remember, many underglazes are more like clay than glaze. But the colors do tend to burn out the hotter they are fired [yellows are notorious for burning out]. Some underglazes hold their colors better than others at the higher temperatures, so read the description on each color, and test at the temperatures you plan to fire to.

Tuesday, December 13, 2016

2017 Winter Classes

Winter classes are starting to be announced!  Check the 'Classes' tab to get the information you need.

Tuesday, October 11, 2016

See what you have been missing? Be bold!

Susan Hickman's Fall 2016 handbuilding class


Often I have been asked which is easier to start out with, handbuilding or throwing?  My  answer "handbuilders are more fearless than throwers when it comes to attaching things" or "handbuilders can think past just making round things, they get crazy in a good way!"

That and it's just fun!

Wednesday, August 10, 2016