[PA-NJ Glassblowers] Coldworking Glass - Information and Instructional Videos
Tony Patti
gaffer at glassblower.info
Sun May 19 14:17:34 EDT 2013
This coldworking information (the many instructional videos below) are from
His Glassworks
and were pointed to by the folks at FusedGlass.org, and I thought it all
was good enough to share.
http://hisglassworks.com/
<http://www.youtube.com/hisglassworksinc>
Many Styles, Many Options
When it comes to coldworking glass, we all do the same thing differently.
Depending on where and who you learned coldworking from, there are a variety
of ways to accomplish the same look in your glass. One is not necessarily
better than the other, only different. We hope to offer as many tools and
accessories for coldworking to fit as many styles as we can and hope to
educate you on what may work best for your process if you're unsure of which
products to choose.
With coldworking you can choose from grinding media like loose grit silicon
carbide, electroplated diamonds, sintered diamond, resin bonded diamond, and
embedded abrasives; all in differing formats. It can be daunting and
perplexing.
Efficiency and Consistency
The biggest upfront difference is price.
Loose grit silicon carbide and has been around as a grinding agent for
centuries. It's easy to use either by hand or with a slurry grinder and is
very inexpensive. It also gives a very nice random "ground" surface
appearance to your glass. This is how many people learned to coldwork their
glass. So why bother with diamonds?
Coldworking with diamonds is far more efficient than loose slurry grinding.
You can generally coldwork a piece in a fraction of the time it takes with
loose grit. Silicon carbide also will break down faster than diamonds so
your grinding surface moves from very aggressive to barely aggressive very
quickly. You have to constantly replenish your grit for accurate grinding.
Diamonds wear slowly so they keep their same level of consistent grinding
for a longer period of time.
Price is always the first thing most people notice. Diamond tools are far
more expensive than their silicon carbide counterparts. What you really need
to consider is your long term efficiency. How much is your time worth and
how many pieces can you complete in how much time?
Depends on the Tool
The difference between Electroplated and Sintered is our most common
question.
Electroplated diamond tools have a single layer of diamond held onto the
tool with a layer of nickel that is grown over the diamond in a plating
tank. Once that layer of diamond is worn down, the tool is used up and it's
time to purchase a new tool.
Sintered diamonds, on the other hand, have diamond impregnated throughout
the entire metal structure of the grinding part of the tool. Once a layer of
diamond is worn down, you can use a dressing stick to drill, slice, or grind
into and it will remove the topmost layer of diamond and expose new diamonds
below. It becomes like a brand new tool!
This begs the question, "Why aren't all diamond tools sintered?"
Most diamond tools will be more effective if they are sintered such as saw
blades, core drills, engraving wheels, and grinding wheels. The problem with
sintered diamond tools is that they do wear down and lose shape. This is not
so important with tools like saw blades and core drills, but engraving
wheels and grinding wheels will oftentimes need to be re-shaped to hold
their profiles. Flat disks perform very poorly as sintered tools as they
will lose their flatness very quickly and need to be dressed very often to
maintain flatness even at the expense of losing perfectly sharp diamonds on
the top layer of the tool.
Same Grits, Different Surface Prep
Resin based diamond tools are more useful for pre-polish than roughing.
When diamonds are electroplated or sintered, they are held in place with a
metal like nickel. When the diamond contacts the glass it doesn't move and
it creates a very deep, aggressive scratch on the glass, even at finer grits
like 500 or 1200. It's still virtually impossible to polish a surface from a
plated or sintered tool even at these finer grits.
When diamonds are mixed into a phenolic resin, they sit in a little pocket
of the resin. When the glass contacts the diamond, the diamond "rolls"
around in that little pocket. So instead of a deep aggressive scratch on
your glass, the resin based diamond gives a smoother, almost buffing scratch
to your glass. This is why you can use a 325 grit diamond in a resin based
material and the surface will come out more like an 800 grit surface and
very easy to polish from.
The biggest mistake people make is trying to use a resin based diamond tool
for rough work. It may work initially, but because the diamond is held in a
small pocket of resin, the harder you grind with it, the faster the resin
will wear down and the diamond will fall out of their pockets reducing the
life of the tool.
Pumice and Cerium
It comes down to the clarity of the polish and the grade of the polishing
media.
The best way to chemically polish your glass is with cerium oxide. Cerium is
a rare earth element that is mined from the earth. It's a naturally
occurring element that you can find listed in the periodic chart. Cerium is
used in a number of industries from filtering water to blocking X-rays. It
also works amazingly well as a polishing media for glass. Used with water to
make a slurry, cerium can achieve an optical polish on your glass surfaces.
How quickly the cerium polishes your glass is dependant on a few factors
like the purity of the cerium (i.e. how much percentage of pure cerium is in
the mixture) and the particle size of the powder. The higher the cerium
content, the faster it will polish the glass. The finer the particle size,
the better the clarity of the polish as well.
Currently, 95% of all the cerium in the world is exported from China. China,
in the last few years, have instituted an export quota on cerium making it
harder and harder to find in the open market. This has driven the price of
cerium up almost 8 times the price it was only two years ago.
One way to extend the viability of the cerium you have is to use another
polishing media called pumice. Pumice is also a very fine particle size
material that works like a polish on your glass. You won't achieve an
optical like finish on your glass with pumice, but it will give what many
refer to as a "dirty polish" to your glass. For many pieces that just need a
quick polish on the bottom of the piece, pumice can suffice as your polish.
You can also use pumice on the surface of your glass, then move to cerium
for a final polish and reduce the amount of cerium it takes to polish and
the amount of time it takes to achieve that polish.
Experience
We work with virtually all the tools we sell.
The people who work here at His Glassworks aren't just a bunch of desk
jockeys. We actually use virtually all the tools we offer. With some
employees having 20 years or more of experience coldworking glass, you can
be sure of getting the best possible advice on your tools and techniques. We
don't sell you a tool and abandon you. With our online video tutorials and
our FAQ section, we try to educate and inform you before and after the sale.
Unlike many places that make tools and have no idea what they are used for
or how they are used or what they will do to your glass, we extensively test
our tools and learn what works and doesn't work for various types of
projects and situations. We can help you make an informed decision on which
tools will work best for your process and which tools might cause you grief.
We're available 5 days a week for any of your problems and concerns.
http://www.hisglassworks.com/cart/cart.php?m=content
<http://www.hisglassworks.com/cart/cart.php?m=content&page=16> &page=16
http://www.youtube.com/hisglassworksinc
Tony Patti
<http://www.glassblower.info> www.glassblower.info
<mailto:gaffer at glassblower.info> gaffer at glassblower.info
<http://www.glassblower.info/qr-code.html> QR Code for Tony Patti -
www.glassblower.info
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