Glazing Overview
Griffith, Turler and Arasteh (2006) described glazing as the process by which uncut spectacle lenses are cut into the
correct shape and fitted into frames. Bray (2011) stated in glazing lenses
are cut into the various shapes of frame available as required by the optician.
Stating that are supplied to the optician in an uncut form (a circular lens
much larger than the final shape needed).
correct shape and fitted into frames. Bray (2011) stated in glazing lenses
are cut into the various shapes of frame available as required by the optician.
Stating that are supplied to the optician in an uncut form (a circular lens
much larger than the final shape needed).
To obtain a particular size used for ophthalmic
purpose they are checked against patient’s records to ensure they are correct
before they are glazed into frame. The lens is measured and aligned. The lens
shape is firstly measured mechanically or optically so that the lens grinding
machine has an accurate image of the lens before cutting begins. The lens is
placed within the machine where the prescription is again checked for accuracy.
Measurements, such as the distance between your eyes and height of your pupil
relative to the frame are entered in to ensure the lens sits exactly in the
correct position in front of your eyes (Newby, 2010).
purpose they are checked against patient’s records to ensure they are correct
before they are glazed into frame. The lens is measured and aligned. The lens
shape is firstly measured mechanically or optically so that the lens grinding
machine has an accurate image of the lens before cutting begins. The lens is
placed within the machine where the prescription is again checked for accuracy.
Measurements, such as the distance between your eyes and height of your pupil
relative to the frame are entered in to ensure the lens sits exactly in the
correct position in front of your eyes (Newby, 2010).
The lens is then placed into the grinding
machine which uses the shape measured earlier to cut off the unwanted material
and edge a groove around the edge of the lens so that it fits snugly in the
frame. If a rimless frame is chosen, the lens goes on to be drilled so that the
frame can be secured to each lens by screws or suction plugs. Finally the
prescription and quality of lens fit are checked before being cleaned and
prepared for they are delivered to patients (Bailey, 2014).
machine which uses the shape measured earlier to cut off the unwanted material
and edge a groove around the edge of the lens so that it fits snugly in the
frame. If a rimless frame is chosen, the lens goes on to be drilled so that the
frame can be secured to each lens by screws or suction plugs. Finally the
prescription and quality of lens fit are checked before being cleaned and
prepared for they are delivered to patients (Bailey, 2014).
Glazing Techniques
The optical laboratory technician inputs the
optical prescription for a pair of plastic lenses in the laboratory’s computer.
The computer then provides a printout specifying more information necessary for
producing the required prescription. Based on this information, the technician
selects the appropriate plastic lens blanks. Each blank is placed in a
prescription tray along with the customer’s eyeglass frames and the original
work order. The prescription tray will remain with the technician throughout
the production process.
optical prescription for a pair of plastic lenses in the laboratory’s computer.
The computer then provides a printout specifying more information necessary for
producing the required prescription. Based on this information, the technician
selects the appropriate plastic lens blanks. Each blank is placed in a
prescription tray along with the customer’s eyeglass frames and the original
work order. The prescription tray will remain with the technician throughout
the production process.
Although the appropriate curves have already been
ground into the front of the lens, the technician must still grind curves into
the back of the lens. This is done in a curve generator. After polishing the lenses,
they are put in an edge grinder, which grinds each lens to its proper shape and
places a bevel around the edge so that the lens will fit the eyeglass frames.
Following any necessary tint applications, the lens are put into the frames.
ground into the front of the lens, the technician must still grind curves into
the back of the lens. This is done in a curve generator. After polishing the lenses,
they are put in an edge grinder, which grinds each lens to its proper shape and
places a bevel around the edge so that the lens will fit the eyeglass frames.
Following any necessary tint applications, the lens are put into the frames.
The plastic blanks have different curves already
ground into the front of them; therefore, the technician must select the blank
that corresponds to the optical prescription required for each lens. The rest
of the optical prescription, or power, must be ground into the back of the
lens.
ground into the front of them; therefore, the technician must select the blank
that corresponds to the optical prescription required for each lens. The rest
of the optical prescription, or power, must be ground into the back of the
lens.
a.
Blocking
Blocking
The technician places the lenses in a lensometer,
an instrument used to locate and mark the “optical centre”—the point
that should be centred over the customer’s pupil—of the lens blanks. Next,
adhesive tape is affixed to the front of each blank to keep the front from
being scratched during the “blocking” process. The technician then
places one lens blank at a time in a “blocker” machine, which
contains a heated lead alloy that fuses the block to the front of the blank.
The blocks are used to hold each lens in place during the grinding and
polishing processes. Next, the technician places each blank into a generator, a
grinding machine that is set for the optical prescription. The generator grinds
the appropriate optical curves into the back of each lens. After this step, the
lenses must be “fined,” or polished (Allen,
2008).
an instrument used to locate and mark the “optical centre”—the point
that should be centred over the customer’s pupil—of the lens blanks. Next,
adhesive tape is affixed to the front of each blank to keep the front from
being scratched during the “blocking” process. The technician then
places one lens blank at a time in a “blocker” machine, which
contains a heated lead alloy that fuses the block to the front of the blank.
The blocks are used to hold each lens in place during the grinding and
polishing processes. Next, the technician places each blank into a generator, a
grinding machine that is set for the optical prescription. The generator grinds
the appropriate optical curves into the back of each lens. After this step, the
lenses must be “fined,” or polished (Allen,
2008).
b.
Polishing
Polishing
The technician selects a metal lens lap – a mold corresponding to
the required optical prescription of the lens, and both lenses are placed in
the fining machine with the back of each lens in the appropriate lap. The front
of each lens is then polished in a series of fining operations. First, each lens
is rubbed against an abrasive fining pad made of soft sandpaper. After a second fining pad made of a smooth
plastic is placed over the original sandpaper pad, the lens is polished again,
as the fining machine rotates the pads in a circular motion while water flows
over the lenses. After the initial fining process is completed, the two pads are
peeled off and thrown away (Stern, 2011).
the required optical prescription of the lens, and both lenses are placed in
the fining machine with the back of each lens in the appropriate lap. The front
of each lens is then polished in a series of fining operations. First, each lens
is rubbed against an abrasive fining pad made of soft sandpaper. After a second fining pad made of a smooth
plastic is placed over the original sandpaper pad, the lens is polished again,
as the fining machine rotates the pads in a circular motion while water flows
over the lenses. After the initial fining process is completed, the two pads are
peeled off and thrown away (Stern, 2011).
Next, the laps are removed from each lens and
soaked in hot water for a few moments. The laps are then attached back on the
lenses and placed in the fining machine, where the third and final fining pad
is attached. The fining machine rotates the pads in a circular motion while a
polishing compound consisting of aluminium oxide, water, and polymers flows
over the lenses (Stookey, 2007).
soaked in hot water for a few moments. The laps are then attached back on the
lenses and placed in the fining machine, where the third and final fining pad
is attached. The fining machine rotates the pads in a circular motion while a
polishing compound consisting of aluminium oxide, water, and polymers flows
over the lenses (Stookey, 2007).
The lenses are removed from the fining machine, and
the block attached to each lens is gently detached with a small hammer. Then,
the tape is removed from each lens by hand. The laps are sterilized before they
are used to hold other lenses. Each lens is marked “L” or
“R” with a red grease pencil,
indicating which is the left and right lens. After the lenses are
again placed in the lensometer to check and mark the optical centre and inspect
the other curves necessary for the proper optical prescription, a leap pad —a small, round metal
holder—is then affixed to the back of each lens (Douglas
& Frank, 2002)
the block attached to each lens is gently detached with a small hammer. Then,
the tape is removed from each lens by hand. The laps are sterilized before they
are used to hold other lenses. Each lens is marked “L” or
“R” with a red grease pencil,
indicating which is the left and right lens. After the lenses are
again placed in the lensometer to check and mark the optical centre and inspect
the other curves necessary for the proper optical prescription, a leap pad —a small, round metal
holder—is then affixed to the back of each lens (Douglas
& Frank, 2002)
Beveling
In bevelling the technician selects the lens
pattern that matches the shape of the eyeglass frames and inserts the pattern
and the lenses into an edging machine. The machine grinds each lens to its
proper shape and places a bevel around the edge of the lens so that the lens
will fit the eyeglass frames. Water flows over the lens throughout this
process. If the lenses require
additional grinding, the process is done by hand using a mounted power grinder.
This step is necessary for lenses to be inserted in metal or rimless frames,
which require more precise bevels.
pattern that matches the shape of the eyeglass frames and inserts the pattern
and the lenses into an edging machine. The machine grinds each lens to its
proper shape and places a bevel around the edge of the lens so that the lens
will fit the eyeglass frames. Water flows over the lens throughout this
process. If the lenses require
additional grinding, the process is done by hand using a mounted power grinder.
This step is necessary for lenses to be inserted in metal or rimless frames,
which require more precise bevels.
Finally, the lenses are dipped into the desired
treatment or tint container. After drying, the eyeglass lenses are ready for
insertion in the desired frames. The optical laboratory may send the lenses
back to the optical outlet without the frames, in which case the optical outlet
will insert the lenses in the frames (Zerwick,
2009).
treatment or tint container. After drying, the eyeglass lenses are ready for
insertion in the desired frames. The optical laboratory may send the lenses
back to the optical outlet without the frames, in which case the optical outlet
will insert the lenses in the frames (Zerwick,
2009).
References
Allen D (2008). Roman
glass in Britain. New York: Shire Publication Ltd.
glass in Britain. New York: Shire Publication Ltd.
Bailey, M. (2014). Oriental glazes. London: A & C Black.
Bray, C. (2011). Dictionary
of glass materials and techniques. Philadelphia: University of Pennsylvania
Press,
of glass materials and techniques. Philadelphia: University of Pennsylvania
Press,
Douglas, R.W. & Frank, S. (2002). A history of glass making. London:
Foulis & Co.
Foulis & Co.
Griffith, B. T., Turler, D. & Arasteh, D. (2006). Surface Temperatures of
Insulated Glazing Units: Infrared Thermography Laboratory Measurements. ASHRAE Transactions102(2):67-9
Insulated Glazing Units: Infrared Thermography Laboratory Measurements. ASHRAE Transactions102(2):67-9
Newby, M.S. (2010). Glass of four millennia. Oxford: Ashmolean Museum
Stern, E.M. (2011) Roman, Byzantine and early medieval
glass 10 BCE–700 CE. H. Cantz, Ostfildern-Ruit
glass 10 BCE–700 CE. H. Cantz, Ostfildern-Ruit
Stookey, S.D. (2007). Explorations in glass: an autobiography. Westerville: American
Ceramic Society
Ceramic Society
Zerwick, C. (2009). A short history of glass. New York: H.N. Abrams Inc.
