Lacquer retarder

Lacquer retarder is the additive to lacquer thinner to retard or slower the drying process of lacquer. Lacquer retarder is usually already mixed in the lacquer thinner to make better flow and smooth film. But in practice sometime we still need to add lacquer retarder in the application. In a certain conditions when the drying time of the lacquer is too fast, or the slow drying is required we may need to add lacquer retarder.
The addition of lacquer retarder is the commonly action when there are some problems associated with the clear coating and finishing film. 

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 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 spray process. At the big product which has large surface area such as a big cupboard or cabinet, then it has high risk to get rough surface since the dust spray. The big surfaces could need long time for spray process and this condition could make the surface that sprayed at first time is dry when the spray process is still on going. The dust spray stick at the dry film and it make a rough film surface.
We can add some lacquer retarder to let the lacquer layer can be wet longer. The wet coating layer will make the dust spray attached is well blended and mix with the lacquer to make smooth surface.

• Streaking finish

Streaking is the lines as a zebra looked in the finishing layer. The streaking at the top coat could be caused by too fast drying. The drying time of lacquer cannot be too fast to let every layer from each stroke of the spray gun can be mixed with previous stroke.
If the streaking problem is caused by too fast drying of the coating, then we need to add the lacquer retarder. The addition of retarder in the mix will make the finishing layer is drying slower thus allowing each stroke spray can be fused and well mixed.

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

Some things to be considered when adding the lacquer retarder.

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 stopped. Too much lacquer retarder is also wasting and also even could  will cause problems. 

•  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.

• Rough finish film.

Long drying time also increases the risk of a rough film surface as a result of the dust that sticks to the wet surface. When the spray room is not clean, then the longer wet surface exposed will make the more dust attached.

• Gloss problem.

The addition of lacquer retarders can also lead to the high gloss finish than it should be. The original lacquer will produce a film with high gloss. The gloss in the lacquer is adjusted by the add matting agent in the mixed. The matting agent is particles that will refract light that come to the surface to make a low-gloss finish film. To reduce the gloss, the matting agent should be in the top surface of the film coating.

Too much lacquer retarder can result too long drying time, and can make the matting agent particles settle on the bottom of the layer film and no more at top of the surface. No matting agent at top surface will make the high gloss film.