Appropriate Material Combinations

The difference between acrylic and alkyd enamels, general application guides, and appropriate material combinations.

Properties of single-component acrylic enamels

Unlike acrylic paints packaged in tin cans, acrylic enamel spray paints are not water-based, but rather have an organic base.

Advantages (compared to alkyd spray paint enamels):

short drying time;
saturated colors;
high elasticity and high adhesion to plastics (due to these properties, acrylic enamels are preferable for applying to plastic surfaces).

Disadvantages (compared to alkyd spray paint enamels):

moderate weather resistance;
moderate adhesion to metals (requires preliminary priming);
moderate resistance to solvents.

Properties of single-component alkyd enamels

The difference between alkyd enamels and acrylic enamels is that the chemical processes within the former do not end immediately after drying. When all the solvent has evaporated, the alkyd enamel polymerization process continues under the influence of atmospheric oxygen. Relatively small molecules, called monomers, join together to form a large polymer molecule, thus making the coating more durable and resistant to various influences, but at the same time less elastic and more brittle. However, alkyds have been known for a very long time and have been thoroughly studied. Peculiarities of the above-said polymerization process are taken into consideration in modern KUDO® formulas, hence even upon complete polymerization, the lacquer film remains quite elastic. The polymerization process can take from several days to two weeks. The coating must not be subjected to mechanical stress during the polymerization process. For example, a car body part painted with alkyd enamel must not be washed and polished for two weeks. Besides, during the polymerization, alkyd enamel must not be coated with other lacquers, even with those based on alkyd, as the coating may be damaged. Either the wet-on-wet coating technique, where additional coats are applied right after the previous coats have dried to touch, should be used, or an additional coat should be applied upon complete polymerization of the previous one. When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization. Alkyd spray paints have high weather resistance and do not require additional varnishing.

Advantages (compared to acrylic spray paint enamels):

high adhesion to metals;
higher hardness;
higher weather resistance;
higher light fastness (fade less);
higher resistance to solvents.

Disadvantages (compared to acrylic spray paint enamels):

longer drying time;
long-lasting polymerization process

Important! Important! Guidelines for selection of materials required for car paint repair can be found on 1K Metallic Enamel Auto Paint and 1K Alkyd Enamel Auto Paint pages.

Table of Appropriate Material Combinations

	Alkyd base	Acrylic base
Alkyd coating	Lacquers must not be applied over an alkyd undercoat during its polymerization, as the alkyd undercoat may swell! An alkyd coat should be applied over an alkyd undercoat either using the wet-on-wet** coating technique, that is, immediately after the undercoat has dried to touch (no later than 1.5 hours after the undercoat has been applied), or upon complete polymerization. *This does not apply to coating over primer! When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization.	An alkyd coat can be applied over an acrylic undercoat after the undercoat has dried to touch.* Or — after the undercoat has dried to handle. Caution! Do not apply alkyd urethane coatings, such as, for example, marine-grade varnish, over single-component acrylic primer, as the undercoat may swell.
Acrylic coating	Lacquers must not be applied over an alkyd undercoat during its polymerization, as the alkyd undercoat may swell. An acrylic coat should be applied over an alkyd undercoat either using the wet-on-wet coating technique, that is, immediately after the undercoat has dried to touch (no later than 1.5 hours after the undercoat has been applied), or upon complete polymerization*. When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization.	*An acrylic coat can be applied over an acrylic undercoat after the undercoat has dried to touch.** Or — after the undercoat has dried to handle.

Alkyd base

Acrylic base

Alkyd coating

Lacquers must not be applied over an alkyd undercoat during its polymerization, as the alkyd undercoat may swell!
An alkyd coat should be applied over an alkyd undercoat either using the wet-on-wet** coating technique, that is, immediately after the undercoat has dried to touch (no later than 1.5 hours after the undercoat has been applied), or upon complete polymerization. *This does not apply to coating over primer!
When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization.

An alkyd coat can be applied over an acrylic undercoat** after the undercoat has dried to touch*.
Or — after the undercoat has dried to handle.
Caution! Do not apply alkyd urethane coatings, such as, for example, marine-grade varnish, over single-component acrylic primer, as the undercoat may swell.

Acrylic coating

Lacquers must not be applied over an alkyd undercoat during its polymerization, as the alkyd undercoat may swell.
An acrylic coat should be applied over an alkyd undercoat either using the wet-on-wet coating technique, that is, immediately after the undercoat has dried to touch (no later than 1.5 hours after the undercoat has been applied), or upon complete polymerization*.
When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization.

An acrylic coat can be applied over an acrylic undercoat after the undercoat has dried to touch*.
Or — after the undercoat has dried to handle.

* Intercoat drying time, dry to touch time, dry to handle time, and the period of time within which the undercoat obtains the maximum mechanical strength properties are given in the Application Guide for each specific product. Alkyd enamels do not require additional varnishing.

** It is recommended that the color of the primer should be as close as possible to the color of the enamel.
When a thick coat of an alkyd lacquer (especially of light shades) is applied over an acrylic undercoat of a bright color, the bright pigment of the undercoat can pop-up. The same is possible when applying an alkyd coating over an alkyd undercoat using the wet-on-wet technique. For example, if a white alkyd enamel is applied over a brownish-red acrylic primer, there is a good chance of getting a pink finish.

Alkyd coating Alkyd base.

Lacquers must not be applied over an alkyd undercoat during its polymerization, as the alkyd undercoat may swell!
An alkyd coat should be applied over an alkyd undercoat either using the wet-on-wet** coating technique, that is, immediately after the undercoat has dried to touch (no later than 1.5 hours after the undercoat has been applied), or upon complete polymerization*. This does not apply to coating over primer!
When the wet-on-wet coating technique is used, adhesion of the newly applied coat is higher than when applied upon complete polymerization.

Acrylic coating Alkyd base.

Alkyd coating Acrylic base.

Acrylic coating Acrylic base.

An acrylic coat can be applied over an acrylic undercoat after the undercoat has dried to touch*.
Or — after the undercoat has dried to handle.

Intercoat drying time, dry to touch time, dry to handle time, and the period of time within which the undercoat obtains the maximum mechanical strength properties are given in the Application Guide for each specific product. Alkyd enamels do not require additional varnishing.