John Baymore on mon 29 jun 98
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From: Marley Wolhud =3Cparishrd=40netway.com=3E
Subject: Re: Seiving glazes
John Baymore, I tried emailing you directly, and it didn't work. What
size mesh do you recommend for theTalisman Sieves?
(snip)
Marley,
Sorry you couldn't get through (see below).
Like most things in ceramics the answer is ....... that depends ( a phrase
that those who take my glaze calc course truly come to HATE =3Cg=3E).
The main purpose of seiving glazes and the like that are made of highly
processed (beneficiated) commercial materials is not to get out unwanted
junk, but to evenly disburse all of the chemisty in the water suspension so
that the glaze is actually mixed well and even in composition. If you use
non commercial materials the story often changes.
Seiving raw wood ash is intended to get out big chunks of unburned stuff,
nails, dirt from the ash pit, and so on. Seiving granite dust is to get
out the pebbles. And so on. That is doing your OWN beneficiation =3Cg=3E.
Different job.
The mesh size you want depends on what you are seiving. As a general rule
(watch those generalizations =3Cg=3E), the finer the better for most glazes.
But there are some glazes and slips (et al) that depend on larger particle
size for effects, and there are some that COME in larger particle sizes
that would have one or more materials seived out if they went through too
fine a seive mesh.
For example, I use a number of wood ash glazes. I use unwashed,16 mesh dry
seived hard wood ash in some of them. Putting the wet mixed batch through
even an 80 mesh seive would let the commercial 325 mesh flint in the batch
go right through and take out a lot of the ash content..... particularly
the little bits of charcoal. I want that stuff in there.
I also use some local granite that I ball mill wet to process it. 99=25 of
that will go through a 100 mesh screen, but too much hangs up on a 120.
Compared to commercial 325 m flint, this is a coarse material.... and gives
the glaze some of it's character.
Too fine a mesh for the condition of your raw materials when they go into
the batch, and you spend time unclogging the seive...... even if the mesh
size of the materials you are using is smaller than the mesh of the screen
you are putting it through. For example, if you have 200 mesh dry
material, but in your locale it gets clumpy due to humidity in storage, and
you try to put it through a 180 mesh screen, you'll have a bear of a time.
Eventually it'll work through.... but not easily. In that case it is
better to use a coarser screen at first....... or as the only one. The
Talisman doesn't clog all that easily, but it can.
If you use all commercial materials ground really fine, and no =
=22granular=22
materials (granular rutile, illmanite, manganese and the like), and you
can't afford to get an assortment of the Talisman screen inserts, then get
the 100 mesh. 100 m is pretty good for most anything (unless you are
making overglazes). I'd really recommend getting an assortment....they're
not that expensive and they give you options.
You can always add the granular materials after seiving the main batch, and
then wet mix like crazy for a long period to disburse the addition.
As to e-mail and my correct address:
Thanks to the miracle of Compuserve, some of you recieve wierd characters
on CLAYART in place of most anything except the main alphanumeric
characters that I type in on my end. So for example, when I type a GREATER
THAN sign, you see something like =3D40 (that was EQUALS 40). Then the =
next
line usually gets a weird line feed with an EQUALS sign at the end.
This is a PIA that I have tried to address with Compuserve for over a year
to no avail. They are (quote....... another character that won't send)
working on it (end quote). There is no provision on the users end to set
the way the messages go out the CIS gateway.
One of the characters that won't come through correct in this case is the
AT sign that looks like an A in a little curlique...... I can't send it
here as an example..... cause it'll get translated to a EQUALS something
for those that have the problem anyway (wg).
SO........my e-mail address is JBaymore ........ followed directly by the
AT sign............. followed directly by Compuserve.com
Looks like the typical e-mail address when printed out...... there is no
unusual equals sign and a number in the middle. Something ..... AT
SIGN....something.
Sorry about the confusion.... that is probably the problem. If that is NOT
what is happening........please let me know.
BEst,
......................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore=40Compuserve.com
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