Hake brushes

Hake (ha-kay) brushes are made from goat's hair. Their advantage over other brushes for applying kiln wash is that they hold a lot of liquid. Proper ones made from joined bamboo work better than the ones with flat handles.

Traditional Japanese hake brush

People often note that these brushes tend to shed hairs. The solution to stray hairs (given to me in a Bullseye workshop) is to invert the new brush and apply super glue at the point where the hairs emerge from the handle.  This holds the hairs in place. It will work on flat handles too.

Inexpensive goat's hair brushes of the hake style.
As can be seen by comparison, there are fewer hairs in these.

Kiln wash application with a brush

Kiln wash is applied thinly in a 1:5 powder to water mix to shelves and moulds.  The object is to get a complete coverage with a smooth surface. 

To ensure full coverage painting four coats is sufficient for excellent coverage.  The kiln was should be applied in four directions – horizontal, vertical, and each diagonal.  This ensures any gaps in one coat will be covered by the others. A broad brush that holds a lot of liquid provides good coverage.  A hake brush is ideal.  The brush should be held almost vertical with the ends of the bristles only touching the surface.

A traditional Japanese hake brush

There is no need to dry each coat before applying the next. It is not like painting your wall. All coats can be applied one directly after the other. No drying between coats is required.  In fact, earlier dried coats tend to make the application clumpy and streaky.

Some people advocate a fifth coat.  I don’t know what the fifth coat is for. What direction other than the four cardinal ones can there be?  It maybe it is insurance that the surface is coated evenly.  This can be checked visually.  The kiln washes used for glass are routinely coloured.  If the shelf shows unevenly through the kiln wash, a little more needs to be brushed onto the more thinly coated area.

It is possible to smooth the kiln washed surface once the kiln wash has a dusty surface – it does not have to be completely dry – you can put a piece of paper between the shelf or mould and your hand.  Gently rub the surface to get a really smooth finish to your kiln washed shelf.

 

More information:

https://glasstips.blogspot.com/2009/08/applying-kiln-wash.html

https://glasstips.blogspot.com/2009/08/smooth-kiln-wash-on-shelves.html

Hake brush

Bamboo handle hake brush

The hake (pronounced hah–kay) brush was developed in the far east.  It has several variations – the original consisted of a group of bamboo brushes bound together in a line.  These are still made and used. Many modern hake brushes have a broad wooden handle with a wide line of hairs.  These brushes are made of very fine, soft hairs - often goat hair is used. 

Flat wooden hake brushes

The flat hake brushes are most often cheaper and in a wider variety of sizes than the bamboo ones.  I prefer the bamboo for the feel in the hand that the broad handle gives.  With the longer hairs, it holds more moisture and delivers even amounts of kiln wash even with long strokes. 

Use

These brushes can hold a lot of moisture and deliver it evenly.  This makes it good for laying  down large areas of even colour in watercolours, and in glass painting. The same characteristic makes it very good for coating shelves with kiln wash.  The brush should be filled liberally with the paint or kiln wash. The brush should be gently shaken to remove any excess. Hold the brush nearly vertical and let the bristles barely touch the surface as you move along in smooth sweeps across the surface.  This allows the kiln wash to be evenly spread with very few brush marks.

Maintenance

One drawback of these brush is that the fine soft hairs are difficult to bind into the ferrule.  This results in the brushes often shedding hairs onto the shelf as it is being coated. A tip I learned from Bullseye is to treat the new hake brush with superglue at the base of the hairs. It does not have to be super glue.  It can be any runny glue, or diluted PVA.  I prefer super glue, even though it is reported to have some sensitivity to moisture. You can work the glue into the centre by using a needle to poke at the hairs to move the glue toward the centre of the bristles.  The glue binds the hairs in addition to the binding at the ferrule, and so keeps the brush from shedding. 

I did this on my bamboo handle hake brush a couple of years ago and it is not yet shedding hairs during applications of kiln wash.

Make sure you clean the bristles immediately after using to avoid any material drying among the hairs and causing them to break when next used.  To clean the brush, you only need running water run through the bristles.  Do not scrub the bristles against anything.  The hairs are delicate.  Set the brush aside horizontally to allow water to drip off and the hairs to dry.  Setting the brush upside down when wet allows water into the bindings of the hairs.  Putting it with the hairs down onto a surface deforms the hairs, making it difficult to straighten them later.

A hake brush is among the most useful tools to put kiln wash onto shelves and moulds because it holds so much moisture.  It does require maintenance to ensure the hairs do not shed and that the delicate hairs are not broken.

Smooth Kiln Wash on Shelves

There are a number of ways of applying separators to the kiln shelf.
These go by a variety of names - kiln wash, shelf primer, batt wash, etc. - all are separators to keep the glass from sticking to the shelf. They are all combinations of alumina hydrate and china clay (or kaolin or EPK) in various amounts.  The china clay provides a high temperature binder for the alumina hydrate which does not stick to glass.

These are some examples of glass separators.  The Primo Primer has very little china clay, and is easy to remove.  It is particularly good for small casting moulds.

    

The object in applying the separator is to achieve a smooth surface a possible. Remember there will always be some texture because of the particle size of the wash.  For the smoothest surface, use the finest powder you can find.  You can, if you want to spend the time and effort, put the powder into a rock tumbler with ceramic balls to get an even finer powder.  Avoid shelf primer that is intended for ceramics, as it is coarser than that sold as a separator for glass.

It also is important to prepare the mixture some hours before application to ensure all the particles of the powder are wetted.  Immediate use often leads to a gritty surface.

There are several methods for applying the kiln wash to the shelf.  The two I use are spraying and brushing.  Which I use depends on circumstances - spraying requires more set up time.


Spraying the separator onto the shelves can give an even coating without brush marks, runs or ridges.  In this example a mould is being sprayed.  To ensure an even covering on a shelf, it should be horizontal and leveled so the kiln wash is evenly distributed.  Numerous light passes with the sprayer is best, as in air brushing.

Applying the kiln wash with a very soft brush such as a hake brush in a variety of directions will ensure full coverage. 

The brush should lightly touch the shelf and provide a number of thin layers.  Applying in four directions - horizontal, vertical, and the two diagonals will ensure full even coverage. There may be some residual brush marks.

To reduce the application marks further, you can brush or spray hot water over the still damp kiln wash. This helps to remove brush marks or the stippling that often comes from spraying and brushing.  It is important that the shelf is perfectly level for this operation.


Another way to reduce the texture after the shelf primer dries is to lightly polish the kiln wash with a ball of old nylons or rub a flat piece of paper with the palm of your hand over the shelf.  Be sure to remove the dust that may be left behind from this polishing.


Boron Nitride

Another separator that has become popular in spite of its expense is boron nitride, often referred to by the trade name Zyp.  This is a high temperature lubricant for industrial kiln operations that has been adapted for the generally lower glass forming temperatures.  This is not suitable for kiln shelves, as it completely seals the porous surface of the shelf.  It is difficult to go back to the cheaper kiln wash separator as the water of the kiln wash solution will not be absorbed into the shelf, leaving a patchy coverage of the kiln wash.  Although both separators should be renewed after each firing (above low temperature tack fusing) the boron nitride is much more expensive and cannot provide a smoother surface than the shelf already has.  My recommendation is that boron nitride use should be confined to moulds or other surfaces where the glass may slide or move in the forming process.