You guys are right. A bottle of Ethanol, labeled Denatured had the label "contains Iso Propyl Alcohol" and my mind did a glitch.
Just make sure that any denatured Ethanol does not cloud up when added to water. This indicates the possible presence of a denaturant that is incompatible with emulsion making and coating.
IPA has no hardening effects but it does act mildly, as I said above, as an antifoamant and a surfactant. Beware of those brands with oils and perfumes. They can cause coating problems.
Your results are very fine. How do the exposures compare for time and lens opening?