VRP-M / PFG-01

Figure1: Spectral Sensitivity curves for VRP-M (left) and PFG-01 (right).

Figure 2: Characteristic Curves for VRP-M (left) and PFG-01 (right).

Figure 3: Grain Size Distribution Curve for VRP-M and PFG-01.

Figure 4: Diffraction Efficiency Curves for VRP-M and PFG-01.

Characteristic curves of fine-grain red (PFG-01) and green (VRP-M) emulsions, showing spectral sensitivity versus wavelength, are shown in Fig.1. The VRP-M optical sensitivity (to CW radiation) is seen to peak at approximately 75 mJ/cm2 and that of the PFG-01 (to CW radiation) at approximately 80 mJ/cm2.

Fig.2 shows the optical density after exposure by CW radiation and after development versus energy. Grain size characteristics for the VRP-M and PFG-01 emulsions are shown in Fig.3.The diffraction efficiency versus exposure for reflection holograms recorded on PFG-01 (using a CW laser) and on VRP-M (using a pulsed laser) is presented in Fig.4. The maximum diffraction efficiency is seen to be >45% for both emulsions. Material lifetime is more than two years.

The VRP-M and PFG-01 emulsions may be used equally well with pulsed lasers and with CW radiation. In the pulsed laser radiation case the emulsion should be post-sensitized with the technique of latensification. The latensification technique is described below.

Table1 shows a summary of recommended processing schemes for use with VRP-M when exposed by pulsed Neodymium lasers (526.5nm, 532nm) and for use with VRP-M and PFG-01 when exposed by CW Argon or by HeNe lasers. In the case of exposure by CW radiation latensification is usually not necessary.

White-light holograms made on VRP-M have a natural green reconstruction colour that can be easily changed by the technique of colour -shifting using D-Sorbitol (described below). White-light holograms made on PFG-01 have a natural yellow/orange reconstruction colour when using a HeNe laser and the recommended chemistry.

All chemicals necessary for the preparation of the recommended solutions can be obtained from the following companies -
(i) Photographer s Formulary Inc. (www.photoformulary.com),
(ii) Sigma-Aldrich www.sigma-aldrich.com),

For pulsed work one may also use the standard D-19 Kodak developer if 6-8g of Methyl Phenidone is added into the final solution.

The temperature of all solutions described herein is 20 0C

VRP-M &PFG-01 Mastering and Copying with Pulsed Radiation Mastering and Copying with CW Radiation.


20-40 mJ/cm2 60-80 mJ/cm2
COPYING 30-60 mJ/cm2 70-90 mJ/cm2
Latensification Yes If needed
Development SM-6, 2min CW-C2, 2min
Wash Water, 1-2min Water, 1-2min
Bleach PBU-Amidol until clear (~2-3 min) PBU-Amidol until clear (~2-3 min)
Wash Water 5 mins Water 5 mins
Final Wash Water with wetting agent (Agepon) 1min Water with wetting agent (Agepon) 1min
Drying Slow Air Slow Air

Table 2: Recommended Processing for VRP-M and PFG-01.

SM-6 Developer

Sodium Hydroxide 12.0g
Methyl Phenidone 6.0g
Ascorbic Acid 18g
Sodium Phosphate (dibasic) 28.4g
if 12H2O 71.6g
Water to 1.0L

CW-C2 Developer
1 part A + 1 part B

Part A
Catechol 20.0g
Ascorbic Acid 10.0g
Sodium Sulphite (anhydrous) 10.0g
Urea 100.0g
Water to 1.0L
Part B
Sodium Carbonate 60.0g
Water to 1.0L
PBU-Amidol Bleach
Potassium Persulphate 10.0g
Citric Acid 50.0g
Cupric Bromide 1.0g
Potassium Bromide 20.0g
Amidol 1.0g
Water to 1.0L
Potassium Iodide Bath
Potassium Iodide 18.0g
Water to 1.0L
Table 2: Developers, bleach and colour chance bath

Figure 5: Hologram Colour versus
D-Sorbitol Solution Concentration for
exposure @ 526 nm


PFG-01 and VRP-M emulsions have peak sensitivities to exposures in the millisecond regime. In order to obtain optimal sensitivity to exposures different from this regime the technique of latensification must be used.

Latensification is usually done directly after the holographic exposure. Before applying the process a latensification time appropriate for your system must be worked out. This procedure is as follows: Place a 25W white lamp at a distance of 1m from a test holoplate or film such that its light uniformly illuminates the emulsion. You will need to try several exposure times.

First of all you will need to develop the unexposed emulsion under normal safelight conditions. The plate will darken a little. This is called the  fog level. After development wash this control plate, dry and keep it handy. Now a series of exposures with small test plates must be made. Start at about 2 secs and go up to around 10 secs. After each exposure develop your plate and match the darkening of this plate to your control plate. If it is the same, more exposure is needed so go back and repeat the process. Stop when a result that is just marginally darker than the fog level is obtained. This is then the correct latensification exposure for your geometry.

Now that the proper latensification time has been discovered, after every proper holoplate exposure you must take your plate and illuminate it exactly as described above for the time that you have worked out. Then all processing is as normal.

Latensification stabilizes and enhances the latent image formed by the holographic exposure. If required, chemical processing may be done with significant delay after latensification (~8 hours).

Colour control

For the VRP-M emulsion we recomend two colour shifting techniques. One produces a fixed colour-shift towards the red of approximately 50 nm. The other produces an adjustable colour shift.

The fixed colour shifting is accomplished by soaking the final hologram for 1 minute in a bath of Potassium Iodide solution. Adjustable colour shifting is accomplished by soaking the hologram for 1 minute in an aqueous solution of D-Sorbitol (sugar substitute - C6H14O6) with added wetting agent. The colour of the final hologram depends on the solution concentration (Fig.5). After soaking, the film must be taken out and put onto a flat  surface. Water drops must be removed using a rubber wiper such as a windscreen wiper. Here one must be delicate - if too much force is employed you may obtain a somewhat different colour than that predicted by Fig. 5. If, after drying of the hologram, the replay colour achieved is not satisfactory, the film or plate may be washed in warm water and then soaked anew in another D-Sorbitol solution of different concentration.





Sigma Aldrich code

Fluka code


Sodium Hydroxide


S 0899





P 3441



Ascorbic Acid


A 7506



Sodium Phosphate (dibasic)


S 0876





C 9510



Ascorbic Acid


A 7506



Sodium Sulphite (anhy.)


S 8018





U 1250



Sodium Carbonate


S 7795



Potassium Persulphate


P 9392



Citric Acid


C 0759



Cupric Bromide





Potassium Bromide


P 9881




(NH2)2C6H3OH" 2HCl




Potassium Iodide


P 8256



Formalin 37%


F 1635


Table 3: Chemical Formulas and suppliers codes.