The Lab

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Dust Hoods

Keeping your work area dust free is a prime consideration when making your own emulsions. HEPA work stations are commercially available but are expensive. A home made work station can be easily made.


John Pecora built this nice bench top Dust hood for DCG plate coating. On the left is the front view and on the right is a side cross section. For the back wall he used a plastic material that looks like square tubes with a screen covering.


This is a Commercial HEPA work station made by NuAire. It has pre-filters on the bottom with a squirel cage blower and the entire back of the work area is one large HEPA filter (4' x 3'). There are four 4' flourescent bulbs in the top.

In order to make sure there are no air vortexes that can trap dust it is important to have the air flow over the entire bench in a laminar fasion. In order to insure a laminar flow the air needs to be directed through a parallel series of tubes. A bunch of straws work perfectly. In order to test the flow one can take a candle and put the flame in different places in the work area. Places where the flame flickers have turbulence and are unacceptable.

Fume Extraction

Processing with formaldehyde and alcohols are common in processing holograms. The fumes are dangerous and provisions should be made for venting them saftly outside. A simple bathroom fan is insufficient. Commercial suppliers like McMaster Carr and MSC Industrial have explosion proof fan assemblies in the $500 range. A good rule of thumb is to have enough venting to exchange the complete air in your room 30 times per hour. Check your local regulations for more requirements.

Processing Areas

The processing are needs to be designed with a few considerations:

  • Light tight
  • Washable surfaces
  • Dust free
  • Running water
  • Lockable chemical storage
  • Counter space for processing trays

Safe lights

In order to see while you are working it is important to have some light. Fortunately if you are using film that is only sensitive to red you can make a green safelight. You should test your safelight before you use it. If you are using long settle times it is wise to make sure no safelight hits the bench during the settle period.

Testing Safe Lights

Do a preliminary test of reflecting the light off of a diffraction grating, CD or DVD. Shine the safe light at the grating and bounce the reflection back to your eyes. If it looks the same then you are looking at the zero order reflection, rotate the grating or CD until you see a reflection that looks like a rainbow. This is a higher order reflection. If you can see red in this reflection then your light is not safe.

Exposure Test

The next test is to get out a piece of your film. Find the uncoated side. Place a piece of electrical tape down one side to make a test patch that has not been exposed. Put the film about a foot from your safelight with the tape facing the light. Add one piece of tape at 15 seconds, 30 seconds, 60 seconds, 10 minutes, 30 minutes. At 60 minutes put the plate in developer. If your plate turns completely black then your safelight is not usable. If only the 60 minute or 30 minute lines develop you are probably OK.

Safe Light Types

For Red Sensitive Film

  • Lime Light: The easiest light to use is a "Limelight" night light. It is very low power and mostly green. If you add a Rosco Gel #90 available from a theatrical supply shop it will be very good but very low power. Attach the gel with electrical tape. John Klayer uses a row of gelled Limelights above his bench.
  • Kodak Safe Lights: Kodak makes a #7B and #3 green saflelight filters (#3 is recommended by Shoebox Holography) suitable for red sensitive holographic films.
  • Home Made Lights: Just using a piece of Rosco #90 (Theater Gel) over a conventional bulb is not enough. Use two layers of #90 or better to have one layer of #90 and one layer of #95. #95 lets in too much deep red to use alone and #90 lets in too much yellow that the Slavich materials are sensitive to.
  • MiniMag Flash Light: Use Two layers of Rosco #90 or better yet one layer of #90 and one of #95 for red sensitive film.
  • T40 EncapSulite fluorescent bulb covers can be used for holographic safelights.


For general information about Safelights see:

Kodak Safe Lights