In my first two blogs, I discussed that lacquer thinner is actually a combination of different chemicals.  These chemicals fall into two categories.  They can be diluent solvents and, thus, dilute the nitrocellulose and/or other resins or they can be active solvents that assist the coating in getting from the spray tip to the surface and then to help it lie down into a smooth, even film.

TABLE

Lacquer thinner chemical listing

The reason for the CAS number is to clarify which chemical is which. These numbers are unique whereas the chemical names are not.


That being said, let’s look at lacquer thinner and see what those chemicals might be and how different combinations or proportions of chemicals affect the drying time of the coating.  Remember, our decision about adding lacquer thinner to a coating is not all about thinning the product.  It is also about affecting how or when the coating will dry.  Our goal is to keep it from drying too soon…like between the time it leaves the spray tip and the time it hits the surface.  On the other hand, we want to have the coating dry in reasonable time so we don’t want the coating to remain wet or tacky for hours after it reaches its forever home.

ARTICLE

Lacquer thinner is lacquer thinner... right?

I wish I had a nickel for every time I have heard those words either as a rhetorical question or a bold statement of fact. In the 21st Century when lacquer coatings are very high tech, the answer is almost always a resounding no.

 

Here is a list of different blends of lacquer thinners.  The chemicals and the CAS (Chemical Abstracts Service) numbers that are in each blend are taken from the MSDS sheet for the blend.

Thinner #1 - 50° - 70° temp. range

   

 

25%

Light Alaphatic Hydrocarbon Solvent

64742-898

3.9

33%

Tolunene

108-41-4

1.5

0.90%

Ethylbenzine

100-41-4

0.7

5%

Xylene

1330-20-7

0.75

4%

Methanol

67-56-1

3.5

10%

2-Propanol

67-63-0

1.7

21%

Acetone

67-64-1

7.7

1%

2-Butoxyethyl Acetate

112-07-2

0.03

       

Thinner #2 - 60° - 80° temp. range

   

 

66%

Toluene

108-88-3

1.5

7%

2Methyl-1-propanol

78-83-1

0.63

2%

2-Butoxyethanol

111-76-2

0.1

10%

Methyl Isobutyl Ketone

108-10-1

1.6

15%

Isobutyl Acetate

110-19-0

1.45

       

Thinner #3 - 90° - 110° temp. range

   

 

10%

2-Butoxyethanol

111-76-2

0.1

20%

n-Butyl Acetate

123-86-4

1

70%

1-Methoxy-2-Propanol Acetate

108-65-6

0.39

       

Thinner #4 - Extreme Duty temperature range

   

 

100%

2-Butoxyethanol

111-76-2

0.1

 

The reason for the CAS number is to clarify which chemical is which.  These numbers are unique whereas the chemical names are not.  It is not unusual for different manufacturers to have their own brand names.  The names will change but the numbers will not.  Sometimes that is a good thing.  For example, p-Chlorobenzotrifluoride is commonly known as Oxsol 100 if for no other reason than that it is easier to pronounce.

Take a look at the number in the right-hand column.  This is the numerical evaporative rate of that chemical.  This rating system always compares chemicals to n-Butyl Acetate, which is always regarded as 1.  The lower the number, the slower it evaporates.  The higher the number, the faster it evaporates.  Thus, acetone has an evaporative rate of 7.7 and 2-Butoxyethanol is 0.1.  Acetone evaporates much faster than 2-Butoxyethanol.  You may know this chemical by the name Butyl Cellosolve.

The point of all this is to quantify how these chemicals will work together to affect the application of the coating.  Acetone is a very fast evaporating solvent.  It is not going to hang around very long on a warm day and help the coating to remain liquid.  Butyl Cellosolve, by contrast, is going to hang around the longest.  To that chemical, in this blend, we will give the designation of being the “tail solvent,” the last one to leave.  This is the one that will affect how quickly to coating will tack up and dry.  The higher it’s concentration in the blend, the slower that this event will come about.

Until next time, spray on!