Dry Raku Glaze Mixing Instructions
Establishing the correct water to dry material
ratio in Raku glazes can be challenging, but by utilizing a process
called slaking, the challenge can be met. Slaking simply means mixing
the glaze’s dry materials in a bucket with enough water to allow
all the dry particles to achieve maximum absorption. Follow these
steps: slake your Raku glaze approximately 24 hours—long enough
that the glaze settles to the bottom of the bucket and the “unabsorbed
water” is clear, not cloudy. At this point, remove most of the
clear water leaving 1/4" to 1/2" on top of the glaze. Mix
thoroughly and allow glaze to sit for another 24 hours.
After the second 24 hour settling period, mix the glaze thoroughly
to a consistency a little thicker than your final use consistency.
To achieve this desired consistency, you may need to add a small amount
of water but always stir the mix thoroughly prior to adding any water
(see "thixotropy" below).
Strain the mix through a 30 to 40 mesh sieve into another bucket,
then strain again back into the original bucket. You should be able
to feel the glaze thin out as you mix it because of the thixotropic
characteristics of the gerstley borate included in most Raku glazes.
Thixotropy is "the property exhibited by certain gels of becoming
liquid when stirred or shaken" (Webster). This makes it important
to always stir Raku glazes thoroughly before considering thinning
with water. It is not unusual for a Raku glaze to become
slightly lumpy even after being strained and mixed. Some ceramists
prefer that their Raku glazes be thicker than other types of glazes.
We recommend running several tests to determine your individual consistency