Techniques for Pouring Microfilm
by Stan Chilton of Chilton's Corner,
as published at Indoor News and Views (INAV)
Over many years other modelers have
asked me how I get the solid color silver and
straw brown sheets of microfilm. I used to
think anyone could produce this kind of film
but I've learned if you don't have the right
equipment, tank and frames, pouring and
lifting satisfactory microfilm sheets can be
Following is my procedure.
The first requirement is a proper size water tank, or pan. I built one out of a 4 x 8 ft..040 thick aluminum sheet, or rather I took the sheet to a sheet metal fabricator and had him make a tank 4" deep by 3' 4" wide and 7' long. The top edges are folded over and the comers are overlapped and riveted, making a quite water tight assembly. This size tank is larger than needed or useable but I tailor the width by means of a 2" x 2" "L" angle aluminum just shy of 7' long so it will fit snugly lengthwise inside the tank so the width can be adjusted to restrict the spread of the microfilm.
A tank larger than 2-1/2 x 7 ft. will allow the poured film solution to spread too far and you will not be able to pour a large enough quantity of solution to get a sheet thick enough to pick up.
I think a tank size of 30" x 72" x 2" deep is just about optimum and should be able to handle sheets up to 12" x 48". The Cadillac of all tanks would be made of .032 to .040" thick stainless steel with welded comers, and a drain plug in one comer.
Some modelers use a 1" x 4" wood framework with a plastic sheet liner. This should work just as well as my aluminum tank, and take less storage space.
MICROFILM FRAMES: I used to use balsa wood frames of about every dimension, whatever I had on hand. But if you're serious about microfilm model flying take the time to build some frames that will assist you in picking up the film colors you want.
Buy some clear 1" thick white pine, any width and strip it into strips about .66" wide. Since the 1" white pine is really only .625 thick your strips are .625" x .66". I use 3 sizes of frames: (all outside dimensions) 10x30, 12x36, and 12x48. The 12" outside width produces a sheet of film wide enough to cover a 9.75" chord wing.
Assemble the frames using Titebond glue and small gussets in the comers. Apply one coat of sanding sealer, sand smooth then spray paint with whatever color of spray paint in cans you have on hand. There is a reason for building these sturdy, heavy frames. If you've ever picked up a sheet of film intact, then had it go splat and disappear, it probably shrunk too fight on the frame. The white pine frames press down on the film sheet on the water and stretch it slightly so you won't lose it after getting it picked up.
An additional benefit is the extra rigidity. Thin sheets are hard to pick up and retain with flexible frames. I make up enough frames so that I can make up a 3 to 4 year supply of microfilm sheets.
But if you already have balsa frames on hand they are useable. To get the balsa frames heavy enough to press down on the poured film I lay a 15" metal drafting machine scale (ruler) across the center of the frame, leave this extra weight on the frame for about 5 minutes to stretch the film before attempting to lift the sheet off the water.
MICROFILM: I have used Erv Rodemsky's various formulas of microfilm and the only one I didn't like was his GP83M and S. I think his current batch is GP-90 which is the easiest of all to pick up. I really liked his GP-84-2P and still use it. I have also used Micro-X Red Label and Lew Gitlow's IMS film. Both these films produce satisfactory sheets, dry and stable, Use whatever product you have the most confidence in. I prefer Erv's batches because they work well for me and I know more about what's in them.
Very important. Any microfilm you purchase that is bottled in plastic bottles should be transferred to glass bottles immediately. Use glass bottles with an aluminum gasket on the lid. Avoid the lids with paper or waxed liners for gaskets. The solvents in the microfilm will escape through the plastic bottles. Very rarely you will need to thin the mixture with acetone but go very slow, thinning only as much as absolutely necessary.
APPLICATORS: I apply the microfilm solution to the water differently than anyone I know. But it's the main reason I can pour solid color sheets in the color and thickness I desire. It also wastes very little microfilm mixture.
I use a glass 5cc hypodermic syringe with a large 2-1/2" long #12 needle. I'd use a larger needle if I could find one. There are other methods of dispensing the microfilm fluid onto the water. Erv Rodemsky uses a short piece of 3/16 or 1/8 brass tubing, filling it with the precise amount of film desired, letting gravity flow the film out onto the water. An added benefit is if the liquid film mixture won't flow evenly out of the tube, it is too thick.
Bernard Hunt uses the same system but with an 8" long graduated approximately 1/4" diameter glass tubing and he varies the orifice by heating and forming the size of the orifice to produce the desired outflow (about.050" diameter). He recently picked up solid silver sheets and 6 out of 7 attempts at gold straw brown colors.
THE WATER: I used to Purchase 3 - 5 gallon containers of distilled water, and still do occasionally, depending on my results with tap water. I bought a charcoal and sediment filter and use these to filter the tap water into the microfilm tank.
Err Rodemsky uses distilled water and saves it for reuse. The distilled water definitely will not leave mineral deposit specks on the film. If the filtered tap water leaves any residue on the first few sheets of film, I immediately switch back to distilled water. Our tap water in Wichita comes from 3 different sources, a nearby lake, drilled wells and underground aqueous beds about 90 miles away. Depending on the particular source, sometimes the filtered tap water works well and sometimes it doesn't. But it's always cheaper than distilled water. The water must be clean and potable, that is you'd drink it.
Be sure the tank is hospital clean. The microfilm solution will not spread well on contaminated water.
TIMING THE POUR:
About 25 years ago I was pouring microfilm and having no luck whatsoever picking up almost any kind of sheet. I decided to call it quits for the evening and came upstairs from my model shop. It was raining outside and I just happened to check the barometer. It was 29.40.
About 3 or 4 days later it was cold and clear, barometer 30.30 and I refilled the water tank. The next morning I lifted 15 sheets out of 15 poured, all in silver and gold, some 12 x 48 sheets.
Since then I wait to produce microfilm until the barometer is at least 30.20 or higher. This condition is normally associated with dryer air, which also may be helping. There seems to be more high pressure conditions in winter than summer. A couple of days before I pour, I disconnect the humidifier from our house furnace, helping keep the air dryer.
PRODUCING THE FILM:
Prior to producing the film you should have on hand sufficient frames, the tank, aluminum divider bar, water, hypodermic syringe and of course, the microfilm solution. Fill the tank 11/2" deep with water. Let stand 6 to 8 hours, or overnight to stabilize in temperature evenness. Make sure the atmospheric pressure stays high. For the amount of film you can dispense on the water through the #12 needle of the syringe, position the divider "L" angle aluminum so your effective water width is 30", times the length of your tank. Different film dispensing methods may require more or less water width, depending on the total amount of film solution laid on the water. Absolutely, the amount of film on the surface area of the water determines the thickness of the film, provided the water surface area isn't too large, and the liquid film has been dispensed evenly on the water.
Fill the syringe with about 2.7 cc's of film. Turn upside down and set for a few minutes for the microscopic bubbles in the film to rise. For a holder, I epoxied a 2 oz. glass jar's base to a 5"x5"x3/8" base of balsa. I cut a piece of foam rubber and inserted it into the jar so the plunger end of the syringe rests on the foam and the syringe flange resets on the top of the bottle. (Syringe is still upside down). The plunger must be supported or it will fall down. Grab a soft hand tissue and cover the needle end of the syringe and top off the film to 2.5cc's of solution.
Standing beside the long dimension of the tank start dispensing the film solution at the left end of the tank and mn a stream down the center, hopefully running out of film at the same time you reach the other end of the tank.
During the pour, the syringe will be held at about a 30 deg angle to the water and the tip of the needle, fried square, held as close to the water as you can without dipping it into the water.
Just enough pressure is exerted on the plunger to let the microfilm solution escape the syringe, evenly and smoothly. If the film on the water has circular stripes, the ejected solution has been forced under the water.
Try again with less plunger pressure.
Dispensing the film solution is a matter of feel and patience. You must use all the film each try and you must lay the Film entirely end of thank to opposite end of tank, at the same time keeping an even dispersion of the film. Keep the same speed traversing the tank every time.
I generally get in the groove of evenly dispensing the film within 4 or 5 trial runs. Even if the laid down solution isn't the exact color and thickness I want, part of it may be, so use one of the smaller frames. When you are comfortable dispensing the film evenly and accurately you can adjust the amount of film in the syringe to get the thickness you want. 2.5 to 2.6 cc's gives me silver, 2.8 or 2.9 cc's gives me very dark blue. 2.7 cc's is straw brown. After I've completed a satisfactory pour I fill the syringe for the next pour, set it in the jar holder upside down, getting ready for the next pour.
Leaving the previously poured film on the water, I take whatever size frame I want outdoors and spray it lightly with 3M 77 contact spray or 3M 75 with a fine spray mist nozzle.
If % the film on the water is silver and the other ½ is blue or off color, I'll use the 10x30" frame and place it on the desired silver end of the water. If the poured film is of even color I'll use the 12x36 frame. Place the sprayed frame gently on the film. Next tear off the excess film outside the frame and remove this debris from the water. Wait about 5 minutes then lift the film and frame off the water. Hold very still just above the water with one corner down to allow the water to drain off. This will take abut 30 seconds, and when mostly dry, carefully set the frame vertically at the other side of the room. The film and frames must be absolutely dry before putting in the storage boxes.
Lifting the film off the water is a technique all in itself. I have heard of some who lift off one end and slide the film and frame lengthwise out of the water. I don't think you can lift silver sheets this way. Lew Gitlow says you need help from the "Lift Angel" to get off good light sheets. I grasp the frame by the ends and pull the frame slowly close to me before I start the actual lift. Then raising the long edge farthest away from me, and a little side to side movement, I move the raised edge further from me and rotate this edge to vertical by the time the trailing edge is leaving the water. Gentle is the name of this game. The most critical times of the lift is the first movement off the water and the free film/frame that is just off the water. The lift movement must be all in one smooth motion -- if you stop or hesitate during the lift all is generally lost.
Ron Higgs lifts the edge nearest him and sometimes gently blows under the film helping it lift off the water. Here again there are slightly different techniques achieving the same result.
After you've set the finished film/frame to one side, the syringe will be ready to pour the next sheet. But before this, examine the water surface and clean it of any residue left from producing the previous sheet.
I use either silver or straw brown for FiD wings, solid silver for stabs and blue for props. Don't worry about the strength of the silver and straw brown film if you are using Rodemsky's film. It is plenty strong enough.
There's probably not much weight saving between gold and blue film. But I know a gold patch on gold film is blue, so gold must be 1/2 as thick as blue. Producing really light solid color film is not easy but is certainly worth it when you hear the nice comments from your competitors about the good looking film. And it probably is lighter.
STORING THE FINISHED FILM:
If you have made microfilm previously you probably already have a favorite way to store the finished frames of microfilm. If you do not have a favorite storage system -- here's mine.
From a wholesale florist I purchased about 8 or 9 large cardboard cartons with shallow top lids. The boxes measure 44-1/2" long, 12" deep and 22" wide. The lid or top fits over the box with 3" overlapping sides. The florist charged me $4 to $7 each. I had to build my own 50" long box to store the 48" long sheets.
For storage the sheets are laid into the box flat with 3/8 x 3/8 x 14" balsa spacers, 2 per sheet. Stacked thusly each box will hold about a dozen frames. Each box is vented to allow free air circulation around the film, but not much. Just under the top lid on each side cut a vent strip about 3/4"x8" and cut the same size strips near the bottom on each end, for a total of 4 vents per storage box. The cardboard boxes can then be stacked ceiling high in one comer of your model workshop, but preferable in another room free of sawdust, etc.