Introduction to Quartz Microscope Slides and Cover Slips:
There are many
microscopy laboratory operations and procedures where UV
transparency is an absolute requirement. There is of course the obvious
case where one might be doing UV microscopy, but there are also other
applications where one is irradiating a sample with UV irradiation and
quartz must be used for the container of the liquid being irradiated.
The window of highest transparency to UV is between 0.15 µm to 5 µm.
Transmittance information for the quartz used for the standard SPI Supplies Brand of quartz products,
GE 124, as well as that for other types of GE quartz is available.
Generally speaking, quartz slides and cover slips are recommended for most applications
involving chemical microscopy, in order to be sure that nothing is "lost" due to absorption
in a glass slide. The use of quartz slides and cover slips are also recommended whenever
UV microscopy is contemplated, including UV confocal microscopy because of the high UV
transparency of quartz.
SPI presents a
very high quality, state of the art, family of clear fused
quartz based products. These items are manufactured from the
very highest purity clear fused quartz. Our vendor-partner making these
items in cooperation with SPI is a leader in the quartz field and uses
proprietary processes that give these quartz products an "edge" over all
others.
Putting it another way, the SPI quartz products are made to the same
standards that are used for quartz products in the electronics industry,
recognized as being the very highest standards in the world.
Some might say this extra quality for more ordinary UV microscopy
applications might be overkill, and perhaps it is, but we don't believe
that this higher quality is necessarily reflected in costs that are going
to be noticeably higher. In any case, veteran researchers often times comment about the
extraordinarily high quality of the SPI Supplies
® Brand of clear fused quartz
slides and cover slips and express their belief that these are the very best quality available
anywhere.
Actually we go beyond what most others can do:
Our superior technology permits us to offer quartz cover slips in Thickness
#0 (0.075 - 0.125 mm thick). We are unaware of anyone else routinely making
such thin cover slips to these specifications of thinness and flatness.
Impact of trace level impurities:
Even extremely low levels of trace impurities can cause some diminution of the
transmittance of the quartz. When the very very ultimate is needed, SPI Supplies
can now offer quartz slides in fused silica, a form of quartz that is even higher
in purity than GE 124. For this highest level of quality in quartz,
we fabricate
in Corning® 7980 fused silica.
Description of the quartz used in these products:
The starting material for all SPI Supplies quartz slides and cover slips is always GE 124
fused quartz. This is the "standard" for the electronics industry and is the top of the
line so far as quartz products are concerned.
Flatness:
This question often times arises and the SPI quartz slides and cover slips
are made to a typical
flatness of 2-4 "bands" per in., but quartz in 1 mm
thickness can bend under its own weight. When placing an optical flat on
top to measure flatness, the slide or coverslip will conform to the flat,
but when on top of an optical flat, it does not weigh enough to flatten
itself out. We are told that slides and cover slips can not be made with
greater flatness than just indicated.
Roughness:
Not to be confused with the term "flatness", the roughness, which is
sometimes referred to as "smoothness", can be measured with AFM and
while we can't guarantee it as a specification, our periodic measurements
with AFM suggest that the typical roughness is better than 2 nm. Some of
our customers are now asking us to supply them with quartz slides that
exhibit a surface roughness better than that. We are now able to offer
the
SPI SuperSmooth™ quartz slides and cover slips with surface roughness
better than 0.5 nm (again, as measured by AFM).
All quartz is not the same! The quartz offered by SPI Supplies is
considered to be the premier quality of quartz and the
full transmittance data is provided to our customers. And
index of refraction data can be equally important for others. We demand that General
Electric Brand of quartz starting material be used exclusively for the production of the
SPI Supplies offered quartz products.
High temperature applications:
The SPI Quartz Slides are often times used as substrates for high
temperature experiments and we are asked about how high in temperature the
slides can be taken before changes occur. That temperature is about 1250°C
(2282°F) as the slide will start to soften at about this point. We do not
have information about how materials being annealed might react with quartz
at elevated temperatures so such experiments should be done cautiously, at
least the first time. For those customers interested, the coefficient of
thermal expansion of the GE 124 quartz (20° C to 320° C) is 5.5 X 10
-7
cm/cm x °C.
Standard thickness specifications:
The standard tolerances for the SPI quartz slides are as follows:
- Standard thickness tolerance: ± 0.005" (127 µm)
- Variation over a batch of slides: Could be as much as 0.005" (127 µm)
- Variation along a single slide: Could be as much as 0.002" (51 µm)
One does not normally see specifications published for quartz slides. We
are obviously confident that these tolerances are far tighter than is
normally found. And for an extra charge, we can provide still tighter
tolerances on the thickness of the slides. Obviously, variation in
thickness can have a deleterious effect on some kinds of data.
But we do apologize for the relatively high cost of these small items
made from quartz, especially when compared to the price of
comparable items in glass. However, the process to make them is an expensive one and there seems
to be no alternative routes to lower priced products that possess the
same high quality. However, despite the high quality of the SPI quartz
products, if you price compare, you will find that our prices are still
lower than most of the alternatives. At the present
time, Thickness #0 (0.075 - 0.125 mm thick) mm in thickness is the very thinnest that these
cover slips can be produced. Note that this minimum thickness starts to increase as
the lateral dimensions of the cover slip increases because the yield (breakage rate)
increases exponentially as the area goes up. We might be able to produce thinner
cover slips, but the lateral dimensions would be very small.
Quartz Microscope Slides
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Thickness: 1 mm (standard)
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Thickness: 0.5 mm (thinner than standard)
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Quartz Cover Slips
The SPI Supplies
® Brand of quartz cover slips are truly a unique kind of product.
They are also made from GE 124 quartz. Only a very small number of production facilities
can make cover slips this thin and yet maintain the parallelism needed between the two
parallel faces. We have listed the largest sizes that we can make without incurring
excessive breakage and making the per piece cost zoom upwards to unacceptable levels.
When our technology advances to the next step when we can offer cover slip thickness in quartz
but in larger dimensions, such availability will be announced on this website page before
anywhere else.
Make sure you select the correct cover glass thickness for your objective.
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Round
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Thickness #2 (0.2 mm thick)
Normal deviation in thickness: ± 0.002" (0.05 mm).
This translates to actual thickness of 0.15 mm to 0.25 mm.
Tighter specifications possible on special request.
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Thickness #1 (0.15 to 0.18 mm thick)
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Square
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Thickness #2 (0.2 mm thick)
Normal deviation in thickness: ± 0.002" (0.05 mm).
This translates to actual thickness of 0.15 mm to 0.25 mm.
Tighter specifications possible on special request.
|
Thickness #1 (0.15 to 0.18 mm thick)
Thickness #0 (0.075 - 0.125 mm thick)
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Friday May 24, 2013
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