The speed of your retarder/reducer is stated as its evaporation rate. This is a number that is compared to N-Butyl Acetate which has an evaporation rate of 1.00. Reducers have evaporation rates greater than 1.00. The larger the number, the faster the speed. Retarders that have an evaporation rate of less than 1.00, the smaller the number, the slower the speed.
For clarity, a retarder is actually just a slow reducer. When adding a retarder to a finish, be sure you sub- tract that volume from the total volume of reducer that you would normally add to avoid over thinning the product. Check your manufacturers specifications for the maximum amount of retarder that you can add. There can be a point where too much can raise the sheen of your finish.
|Solvent||Evaporation Rate||Flash Point ÂºF|
|Methyl Ethyl Ketone (MEK)||3.8||16|
|Methyl Amyl Ketone (MAK)||.4||1.2|
|Propylene Glycol Butyl Ether (PnB)||.8||138|
|High Flash Naptha||..06||150|
The flash point of a material is defined as the temperature at which an ignition source 1 cm from the surface of the liquid will cause ignition. The standard method is defined by ASTM and most flash points are measured in a “closed cup” flashpoint tester. Discrepancies/disagreements are found in the litera- ture for some substances, but the values are usually fairly close