Details:

When Butyrate Dope is used in a high humidity environment, it will sometimes "blush" (meaning it will dry with a dull, milky finish). The best way to prevent blushing is to slow down the rate of drying by using Dope Retarder as a partial substitute for the regular dope thinner.

Use only as much retarder as is needed, to prevent blushing, typically 25% to 100% of the normal thinner requirement.
Dope Retarder should be used only in the last one or two coats of the finishing process.