" " wisno wood furniture finishing: The properties of common solvents.

Monday, October 11, 2010

The properties of common solvents.

Solvents for the finishing material.

Almost all finishing materials need a thinner. Thinner is made from mixture of solvent that is mainly used to reduce the viscosity of the material. How a mixture of thinner is made depends on the type of finishing materials to be thinned. A particular finishing material usually requires a particular solvent or solvent mixture to be dissolved properly. Moreover, usually a finishing material is designed to have a certain character which can also be obtained by the using of a specific of thinner mix as well. Therefore, it is actually advisable to use one set of a finishing material with its thinner. When we buy finishing materials we should buy its thinner which is properly designed to match with the finishing materials.
However sometimes we as a finishing people must also do our own solvent mixing to get the effects as we want. Mixing solvent also sometimes have to do to solve the problems in a finishing process. Most of coating problems such as: pinhole, bubble, orange peel, rough surfaces, etc. can be solved with the thinner adjustment. The problems on the stain and its applications such as: blotchy, stain dry too fast or too slow also much can be solved by arrangement to the thinner used.
Since that we should have some basic knowledge about the properties of the solvents. The knowledge about the properties of solvents is can be used as a guide to set a thinner mixture to obtain the character of mixture as we want.

The properties of solvents.
Solvent are chemicals, that each has its specifics chemical and physical properties. The common properties that we need to know are the properties that have a relation with finishing process. Some of them are: solubility, evaporation rate, density, and flash point.
Solubility is the ability of the solvent to dissolve a finishing material. Solubility is a specific characteristic according with the finishing materials to be mixed. For example, butyl acetate, acetone, methyl ethyl ketone are the excellent solvents for nitrocellulose material, while mineral spirit is a good solvent to the oil finish, oil varnish and glaze. A simple test can be conducted to determine the solubility of a material with a solvent. A particular material tested was diluted with various solvents with the same mixing ratio, and then the effect is observed. A mixture that does not well match will be seen in the mixture appearance. If the resulting mixture is not looked well blended then it means that mixture does not dissolve each other. The mixtures that seem to mix well can be more observed by the measurement of viscosity. A solvent that can quickly reduce the viscosity with less solvent uses is the solvent which has high solubility to the finishing material.
The other important solvent property is the evaporation rate. It is the time needed by the solvent to evaporate in the open room. Evaporation rate determine the speed of drying of a mixture when it is applied. A mixture with high evaporation rate solvent will dry faster than the mixture using the low evaporation rate solvent.
Other necessary properties is the flash point. Flash point is a temperature where the material can generated fire if exposed to sparks. It is related to the safety and security of the solvent. We should avoid the spark when the the flash point of the material is under the room temperature.

Below is the table the properties of common solvent used in the finishing industry.

SolventFlash point (Deg F)Evaporation rate
Methyl alcohol561.6
Ethyl alcohol612.0
Isopropyl alcohol632.4
n-Butyl alcohol970.5
Amyl alcohol1020.33
Methyl ethyl ketone235.7
Methyl isobutyl ketone601.6
Methyl isoamyl ketone960.5
Diacetone alcohol1260.12
Ethyl acetate275.0
Isopropyl acetate443.0
Isbutyl acetate671.5
n-Butyl acetate771.0
Cellosolve acetate1210.3
Ethylene glycol2410.01
Diethylene glycol2900.01
Ethylene glycol monomethyl ether1050.5
Ethylene glycol monoethyl ether1100.3
VMP naphta452
Mineral spirit1050.12

Note: the evaporation number are compared with the evaporation rate of the n-Butyl acetate


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