Q: In a recent column you cautioned against the use of PVC (polyvinyl chloride) plastic film storage materials. I have invested in 100 sheets of plastic pages for storing slides (each page holds 20 35mm transparencies in individual pockets). After reading your column I called the company, 20th Century Plastics, to ask if their PVC plastic was inert. tI was told that it was safe for photographic uses, but they couldn't tell me how they arrived at this assurance. Could you find out?

A: This question of the safe storage of film and transparencies concerns all of us, so I too called 20th Century Plastics. I received a return call from Jon Burke, marketing manager for Reneer Films (P. O. Box 400, Auburn, Pennsylvania 17922 -- an address printed here because he assured me he would like to hear from anyone whose film had been damaged by his product). He told me that Reneer furnished the PVC product for 20th Century Plastics as well as for Polaroid, Kodak and Hallmark Cards. To his knowledge there have been no complaints of any chemical interaction during storage.

My original caution as to the use of PVC was taken from the Eastman Kodak Encyclopedia of Photography in which it's mentioned that PVC plastic may give off hydrogen chloride which can cause image deterioration of color film.

Burke said that Reneer tests the PVC material to be used for photographic storage by placing both prints and color slides between sheets of plastic weighted down by glass so that there is overall contact. This sandwich is then given an accelerated aging process by submitting it to heat of 158 degrees F. for 28 days -- the equivalent of a hot sauna, or 20 years of normal aging at 70 degrees.

After the test period the prints and transparencies are examined visually under a microscope and chemically to determine if there is any weight loss (which would indicate deterioration of the image). He said that their testing shows no deleterious effect.

He added that there's no such thing as a completely inert plastic product -- it's all a matter of degree.

But thee are other factors that effect the deterioration of stored images. Excessive heat, light and moisture are some of the villains, often found in attics and damp basements.

Q: In a recent reply to a reader's query concerning flash on a 126 camera, you got a couple of things wrong. First, you advise the person to take the camera to where it was bought and not to a repair shop "because the cost would exceed the value of the camera." The name of the camera was not mentioned. How did you arrive at that appraisal? The fact that the camera is of Japanese manufacture has no bearing on your advice. And what if the camera were purchased in Japan? What's the cost of returning the camera to the dealer in that case? Then again, how about the service centers set up here by Japanese manufacturers?

The second mistake is a dangerous one. You advised the person to "partly block off the light by holding your finger in front of the flash." Holding your finger in front of a flash cube is dangerous. It can result in a burnt finger. If you don't believe it, try it. Most simple automatic cameras usually have an overexposure syndrome with photos taken at extreme close distances. They seem to work best at distances from 5 feet to 10 feet. After all, you are not working with a Nikon and a professional flash unit.

A: The first error is not all that glaring. The going scale today for camera repair persons is $40 an hour. At that rate it wouldn't take too long to eat up the price of the average 126 camera. My suggestion was to take it back to the shop where it was bought to about an adjustment. That's just common sense.

As for cameras bought in Japan -- well, very few tourists buy 126 cameras in Japan; more likely it's Nikons and other high-priced 35-mm cameras and lenses they have the yen for. And this suggestion was made with the idea that there may still be a warranty on the camera and, if an adjustment is required, the dealer can send it to the nearest manufacturer's repair facility.

You rapped me smartly on the finger for the second mistake -- it isn't safe to hold your finger close to a flashbulb. True. I have used this technique and it works, but certainly I shouldn't recommend it. (My suggestion of a piece of paper over the bulb wasn't too smart, either, as that too could ignite.)