Russ, that is for an anti-halation layer, applied to the back of the film. It might be an undercoat under the emulsion layers, but that is not clear. In any case, the film would have to be washed after application if the emulsion is being coated on it. The residual Sodium Hydroxide would be bad stuff. I advise caution. This forms Sodium Ethoxide which will react with the support and make it more polar. And, more alkaline probably.