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BULLETIN #7 — Newton Rings
A frequent comment concerning ESCO slides is that they are “oily” because the person looking at them sees a rainbow coloration when two slides are held together. Experience has led most people to connect this rainbow effect with an oil slick because this is the most common occurrence.
It is actually caused by refraction of light rays, which are broken up into component colors according to wavelength. In order for this “Newton Ring” effect to occur, the surfaces in question must be clear, transparent, in intimate contact, and almost perfectly flat. Any foreign matter or dirt on the surface of the slides will cause the rainbows to disappear or to lessen substantially. Separating two slides showing the rainbow effect, rubbing one of them with a finger, thereby depositing foreign substances (including skin oils) on the surface, and then placing them back together can demonstrate this. The rainbows will have tended to disappear, although pressure on the two slides may make them appear once more in diminished form.
The lack of oil can also be demonstrated by dipping one of the precleaned slides into water, which will cling to the surface in an even film from edge to edge of the slide. If the user’s finger is then rubbed on the surface of the slide, enough skin oil will be deposited so that then the slide is again dipped the water film will break up into droplets on the now oily surface.
Thus the apparent oiliness shown by the rainbow coloration is actually a proof of the lack of oiliness or foreign matter on the surface of the slides as well as a demonstration of the flatness of the surface.
These precautions will minimize the chances of slides and cover glasses developing problems related to moisture contamination such as sticking and corrosion of the glass surface. Remember that slides do not necessarily have to be old to have been affected by moisture, just that the chance of a moisture contamination increases with the age of the product. Our products are fully guaranteed and we will be happy to replace any product involved in a customer complaint regardless of the age of the product.
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BULLETIN #10 — Storage & Handling
Microscope slides and cover glasses should be rotated. Rotation is the first line of defense against temperature and humidity changes resulting in moisture contamination. They should also be kept off of concrete floors on a pallet. Slides should be kept as far away as possible from doors and heating and air conditioning ducts to minimize temperature and humidity changes.
Slide and cover glass cases should be allowed to come to room temperature in the lab before they are opened.
These precautions will minimize the chances of slides and cover glasses developing problems related to moisture contamination such as sticking and corrosion of the glass surface. Remember that slides do not necessarily have to be old to have been affected by moisture, just that the chance of a moisture contamination increases with the age of the product. Our products are fully guaranteed and we will be happy to replace any product involved in a customer complaint regardless of the age of the product.
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