Comments about Amaco Underglaze Pencils:

I've been using various underglaze pencils, including pencils made from scratch from 5 different recipes for the past 3 years and Amaco's pencils are the best in quality. The underglaze "lead" is harder and consequently more brittle than other manufacturer's "lead" and can be tricky to sharpen. This isn't necessarily a bad thing. It's firmness helps create a stronger and more refined line if desired and lends itself to crosshatching.

The pencils are rated for up to cone 10 and retain their blackness under a thin layer of glaze. at mid-fire to high fire with moderate to high amounts of glaze the quality of line starts to break down as the pigment start to diffuse though out the glaze creating a blurry quality. Under certain glazes, if used generously the pigment can start to take on a navy blue quality.

The pigments in the black pencils will vitrify with out a glaze over them at around cone 7, anything under that temperature will be conducive to smudging.

When drawing on a bisqued piece smudging can be a problem but the hardness of the "lead" causes it to embed in the pours of the clay so the line remains in a lighter form. In other words you can blend with these pencils but you cannot blend to the point of completely obscuring the original line.

The material that these pencils are made of are not at all water soluble. This is both a good and potentially a bad thing. This means that you can pour glaze over the finished drawing with out having to worry about the flow of glaze washing out the drawing you're glazing. However if you have large areas of heavy pigment the glaze won't absorb well and sometimes just slide off of that area; think of water on wax paper. A second dip will almost always remedy that problem but then you might have problems stated above with using too much glaze. It helps if you thin down the glaze you're using from what you probably are used to and just always use multiple layers until you can just barely see the drawing through the glaze.