Lacquer retarder

Lacquer retarder is the additive to retard or slower the drying process of lacquer. Lacquer retarder is usually already mixed in the lacquer thinner to make the good flow and smooth film. But in the finishing process we may still need to add some lacquer retarder in the application. In a certain conditions when the drying time of lacquer is too fast, or the when slower drying is required we may need to add lacquer retarder. 

Here are some finishing problems can be alleviated by the lacquer retarder.

• Blushing.

Blushing is the formation of fog or a rainbow in the film coating. It is caused by the water vapor that is trapped in the coating film during the film forming. Blushing is happened when we do clear coating application at the humid air, for example at the morning, at the night or at rainy days, especially in certain areas which have high humidity.
If there blushing problem, then we can add some lacquer retarder into the top coat mixture to slow down the drying process. The slow drying process will allow water vapor trapped in the coating film to release and come out from the film layer.

• The rough surface of the film layers.

The surface layer of a finishing film may be rough due to the dust spray that is attached to the film surface during the spray applications. Dust spray could happen because there are some surfaces area that has been dry during the spraying process. This dust spray problem could be occurred at the big product which has large surface area such as a big cupboard or cabinet. The big surfaces could need long time for the spray; the surface that sprayed at first time could be already dry when the spray process is still on going. The dust spray stick at the dry film and make a rough film surface.
We can add some lacquer retarder to let the lacquer layer be wet longer. The wet coating layer will accept the dust spray to be mixed and solved with the lacquer. There will be no dust spray and the smooth film surface is resulted.

• Streaking finish

Streaking is the lines as a "zebra looked" in the finishing layer. The streaking at the top coat could be caused by the top coat layer is drying too fast. The drying time of lacquer cannot be too fast to let every layers of the film coating from each stroke to solve  and mixed with its previous stroke.
We can add the lacquer retarder to solve the streaking problem that is caused by too fast drying. The addition of retarder in the top coat will slow down the drying time of the top coat layer thus allowing each stroke spray can be fused and well mixed.

How to make lacquer retarder?. 
 
Lacquer retarder is made of solvents that has high solubility to the lacquer, but have slow evaporation time. Some commonly used solvent for the lacquer are: butyl acetate, cellusolve acetate, butyl cellusolve, p.m. methyl acetate. 

Although it can help a lot, but too much retarder is not recommended. The addition of lacquer retarder should be undertaken only on special case, in the normal condition the addition of lacquer retarder should be avoided. Too much lacquer retarder is wasting and even could cause for finishing problems.

Some problems that could be generated by too much retarder. 

•  Longer drying time.

The addition of retarder will slow down the drying process and it will make the overall finishing process becomes slower. It could be disadvantage in the big volume finishing industries that do finishing job in big volume. The slow drying process is also raise the risk to get the soft finishing layer problems.

• Rough finish film.

Long drying time also increases the risk of a rough film surface as a result of the dust that sticks at the wet surface. The longer wet surface exposed will lead to the more dust attached. This condition will raise the rough problem for the rough finish, especially when the finishing and drying room is not quite clean and free dust.

• Gloss problem.

The addition of lacquer retarders can also lead to the high gloss finish than it should be. The gloss in the top coat is adjusted by the add matting agent in the top coat mixed. The matting agent is particles that will refract light that come to the surface to make a low-gloss finish film. See our article: matting agent in the top coat.
To work optimally, the matting agent should be stay in the top surface of the film coating. The matting agent at the bottom layer make it does not work to refract the the light and affect the film gloss. Too much lacquer retarder can result for too long drying time, and let the matting agent particles to settle at the bottom of the layer film, and the result is the high gloss finishing film.