A SciGB asks for Hot glass help with glass molds.

A SciGB asks for Hot glass help with glass molds.

Post by PWalthe » Thu, 07 Nov 1996 04:00:00



Greetings to all!
      I am trying to reproduce "bowls" -  similar to sediment bowls
found on the carburetor of early gasoline/oil engines. These are in
various sizes, up to a diameter of 3". I have had the use of a cast
iron split mold, of 1"size. A press/blow mold, this allowed for an
interesting learning experience.
      The task is to fabricate blow molds in a variety of sizes at a
reasonable cost. Cast iron is the material of choice however the cost is
justified only if there is a need for many pieces. I would like to
explore slip casting using a castable ceramic. There are a number of
formulations available however the costs are such that much could be
spent in experimentation finding the right product.
      I would be very grateful to hear from anyone who may have had
experience with such products. I also welcome any input on what you may
feel is a better approach to the problem. It would be a delight to hear
from our colleagues in the hot glass community.
Many thanks,   Bob

(Robert G. Campbell)

 
 
 

A SciGB asks for Hot glass help with glass molds.

Post by stack.. » Fri, 08 Nov 1996 04:00:00


On 1996-11-06 pwalther1 said:
   >Greetings to all!
   >I am trying to reproduce "bowls" -  similar to sediment bowls
   >found on the carburetor of early gasoline/oil engines. These are in
   >various sizes, up to a diameter of 3". I have had the use of a cast
   >iron split mold, of 1"size. A press/blow mold, this allowed for an
   >interesting learning experience.
   >The task is to fabricate blow molds in a variety of sizes at a
   >reasonable cost. Cast iron is the material of choice however the
   >cost is justified only if there is a need for many pieces. I would
   >like to explore slip casting using a castable ceramic. There are a
   >number of formulations available however the costs are such that
   >much could be spent in experimentation finding the right product.
   >I would be very grateful to hear from anyone who may have had
   >experience with such products. I also welcome any input on what you
   >may feel is a better approach to the problem. It would be a delight
   >to hear from our colleagues in the hot glass community.
   >Many thanks,   Bob
   >(Robert G. Campbell)

  I don't know if this is directly applicable, but I do sagging into
slip-cast molds all the time.  I also create molds from a cone 04 white
sculpting clay.  Fire it to bisque, apply a thin coat of kiln wash (also
called shelf primer) and go to it.  I imagine that, with proper care,
a slip cast mold could last indefinitely.  The biggest danger is to allow
the glass to come in contact with the bisqueware.  If that happens, it
welds itself right to the mold, and when you separate the two, part of the
mold will stay attached to the glass. -- this won't happen as long as
the mold is completely covered with kiln wash.
  I don't know what kinds of temperatures you're talking about, but most
of my sagging takes place at around 1300F., and I occasionally do a
simultaneous fuse and sag, which takes it up to around 1550F.  Bisqueware
molds are ideal for this kind of work.

  NOTE:  The kiln wash often imparts a cloudy look to those areas of the
glassware which were exposed to the most pressure.  If you need absolute
optical clarity, I don't know that this is the route to go.

 - Steve Ackman
   Metamorphosis Glassworks
   Strafford, N.H.

`[1;32;45mNet-Tamer V 1.05.1 - Test Drive

 
 
 

A SciGB asks for Hot glass help with glass molds.

Post by Michael Olse » Fri, 08 Nov 1996 04:00:00


Quote:

>   NOTE:  The kiln wash often imparts a cloudy look to those areas of the
> glassware which were exposed to the most pressure.  If you need absolute
> optical clarity, I don't know that this is the route to go.

I'm not sure if this would work, or exactly how to go about it, but I
have frequently used Aquadag (available from Wale [800-444-WALE] and Ed
Hoy [800-HOT-GLAS]) as a 'resist' and 'release' agent for borosilicate
work, especially for coating mandrels when doing vacuum redraw.  I'm
suggesting Aquadag (cut about 3:1 or 4:1 with DW) because it results in
an unusually smooth surface that can actually be *polished* with a piece
of notebook paper.  The underlying form should be as smooth as possible,
of course.

Michael

 
 
 

A SciGB asks for Hot glass help with glass molds.

Post by stack.. » Sat, 09 Nov 1996 04:00:00


On 1996-11-07 glassguy said:

   >> glassware which were exposed to the most pressure.  If you need
   >>absolute  optical clarity, I don't know that this is the route to
   >go.
   >I'm not sure if this would work, or exactly how to go about it, but
   >I have frequently used Aquadag (available from Wale [800-444-WALE]
   >and Ed Hoy [800-HOT-GLAS]) as a 'resist' and 'release' agent for
   >borosilicate work, especially for coating mandrels when doing
   >vacuum redraw.  I'm suggesting Aquadag (cut about 3:1 or 4:1 with
   >DW)

  I assume that DW in this context means "distilled water."

   >because it results in an unusually smooth surface that can
   >actually be *polished* with a piece of notebook paper.  The
   >underlying form should be as smooth as possible, of course.
   >Michael

  Well, my dialing finger is getting warmed up right now...  Thanks.

  - Steve

`[1;34;44mNet-Tamer V 1.05.1 - Test Drive

 
 
 

A SciGB asks for Hot glass help with glass molds.

Post by Geof » Sun, 10 Nov 1996 04:00:00



Quote:

>On 1996-11-06 pwalther1 said:
>   >Greetings to all!
>   >I am trying to reproduce "bowls" -  similar to sediment bowls
>   >found on the carburetor of early gasoline/oil engines. These are in
>   >various sizes, up to a diameter of 3". I have had the use of a cast
>   >iron split mold, of 1"size. A press/blow mold, this allowed for an
>   >interesting learning experience.
>   >The task is to fabricate blow molds in a variety of sizes at a
>   >reasonable cost. Cast iron is the material of choice however the
>   >cost is justified only if there is a need for many pieces. I would
>   >like to explore slip casting using a castable ceramic. There are a
>   >number of formulations available however the costs are such that
>   >much could be spent in experimentation finding the right product.
>   >I would be very grateful to hear from anyone who may have had
>   >experience with such products. I also welcome any input on what you
>   >may feel is a better approach to the problem. It would be a delight
>   >to hear from our colleagues in the hot glass community.
>   >Many thanks,   Bob
>   >(Robert G. Campbell)

>  I don't know if this is directly applicable, but I do sagging into
>slip-cast molds all the time.  I also create molds from a cone 04 white
>sculpting clay.  Fire it to bisque, apply a thin coat of kiln wash (also
>called shelf primer) and go to it.  I imagine that, with proper care,
>a slip cast mold could last indefinitely.  The biggest danger is to allow
>the glass to come in contact with the bisqueware.  If that happens, it
>welds itself right to the mold, and when you separate the two, part of the
>mold will stay attached to the glass. -- this won't happen as long as
>the mold is completely covered with kiln wash.
>  I don't know what kinds of temperatures you're talking about, but most
>of my sagging takes place at around 1300F., and I occasionally do a
>simultaneous fuse and sag, which takes it up to around 1550F.  Bisqueware
>molds are ideal for this kind of work.

>  NOTE:  The kiln wash often imparts a cloudy look to those areas of the
>glassware which were exposed to the most pressure.  If you need absolute
>optical clarity, I don't know that this is the route to go.

> - Steve Ackman
>   Metamorphosis Glassworks
>   Strafford, N.H.

>`[1;32;45mNet-Tamer V 1.05.1 - Test Drive

Hi. some ompanies in the uk use hardwood moulds for blown glass
development work. Pearwood is prefered but i suppose that any fine grain
wood could be used. they are used wet and have a limited life time.
Graphite is also used but is more expensive. Both can be turned on a
lathe for shaping.
There are other mould materials used in casting like 50% plaster/silica
but i do not know if these can be used for blowing. Hope this helps.
--
Geoff
 
 
 

A SciGB asks for Hot glass help with glass molds.

Post by RD Dalb » Sun, 17 Nov 1996 04:00:00


I work extensively with molding systems for casting molten glass and
have quite a bit of experience in the off-hand and SciGB techniques in
glass.

It seems apparent that you work with a lathe.  I would probably make
the sediment bowls on the lathe by closing off the end of tubing that
is of the diameter needed.  Then torch off the tube to the length
needed and fire polish, flare, bead or square off the open end as
needed.  If tight tolerances are required, a drag bar for the lathe
can be set up with graphite pads to shape the closed end.  For the
open end, a shaping tool or drag bar can also be used.

If you are wanting to free hand the sediment bowls,  such as with
off-hand techniques, graphite can be shaped on a wood or metal lathe
to the shape required and used as a blow mold.

With regard to ceramic based materials, I have tried several different
materials and never had good results with respect to repeatability.
With the use of any ceramic type material, mold releases become a very
important issue.  I have always come back to surface treating the
ceramic with graphite washes building up a sufficient layer to prevent
glass fusing to the ceramic materials.  For short order, easily shaped
objects, I always seem to come back to synthetic graphite.

If you like the process of metal molds, but not the cost of cast iron,
try bronze.  Bronze works pretty well and is generally cheaper and
easier to finish.  For the simple shape of a sediment bowl, graphite
should work well enough.

I am interested in ceramic based mold materials for certain kinds of
applications.  Any experience or insight with regard to ceramic based
molds that you would like to discuss is encouraged.

RD Dalbey
GlassWorks Foundry