How to Make a Phosphor Screen

Prepare the screen to be coated by gently wiping it with a cloth. If this is a fresh screen, not much wiping will be required. If this is a used phosphor screen to be recoated, more wiping may be needed to remove any existing coating. Degrease the screen by applying methanol or acetone. Prepare the screen with a pickling solution so that the phosphor will adhere properly to the screen. For stainless steel screens, this can be a solution of HNO3 and HF that the screen is immersed in for 30 to 60 seconds or a solution of HNO3, HF, HCl and warm water in which the screen is immersed in an ultrasonic bath for five minutes. For an aluminum screen the screen should be dipped in a 6 percent HF solution for 20 seconds, rinsed with water, then dipped in a 32 percent HCl solution for 60 seconds. If the screen turns black in the HCl, repeat the dips in both acid solutions.

Prepare two solutions for the phosphor coating. The first will contain 1 cup to 2 cups of water and .06 ounces of an electrolyte solution Ba(NO3)2. This should be prepared in a Erlenmeyer or volumetric flask. Shake this flask vigorously by hand for two minutes, then place in the ultrasonic bath and keep at room temperature until ready for use. Shake the solution again immediately before use. The second will contain 1/2 cup to 3/4 cups of water with .006 ounces of silica gel and .11 ounces of phosphor, which should also be prepared in an Erlenmeyer or volumetric flask, shaken vigorously and placed in the ultrasonic bath for five minutes. Cool the bath or shake the flask, then place in bath for another five minutes.

Transfer the second solution to a large Erlenmeyer flask. Add the first solution to this flask as well. Shake vigorously by hand for one to two minutes. Pour the solution into a 3 quart to 4 quart beaker. Rinse the flask several times with water and add this rinse to the beaker. The beaker should be filled to 3 quarts with water. Use a large stirbar to stir the solution rapidly for five to 10 minutes. Cover the solution and let it settle for 10 minutes. Pour most of the solution into another large beaker leaving behind some liquid and the larger settled particles at the bottom of the first beaker. Cover the second beaker and let it settle for seven minutes.

Place the sedimentation beaker on a ringstand or other stable surface. Use three hooks made from stainless steel wire to suspend the screen three-quarters of the distance to the bottom of the beaker. Pour the decanted solution into the sedimentation beaker through a funnel that is pointed away from the screen. Make sure to pour the solution evenly and continuously. Let stand for five to 12 hours or until very clear. Adjust the stopcock to allow the solution to drip out, and set the flow rate to allow the solution to drain out in six or more hours.

Allow the screen to dry for several hours after the solution has drained in the covered beaker. Inspect the screen to see if the surface looks even. If there are uneven patches due to problems with the draining of the solution, the above steps may need to be repeated. If the screen looks to be evenly coated, remove it from the sedimentation beaker and bake at 176 degrees Fahrenheit for 30 minutes.