More and more people, not being professional painters, decide to change the color of their homes. Inspired by friendly low-VOC or zero-VOC latex paints, as well as popular Dulux paint ads, they paint a room in one afternoon without covering most furniture or floors with protective film, or not covering them at all.
In order to make painting a pleasure for them without having to wash off paint dots from furniture, floors and themselves, the challenge for paint producers is to produce paints that do not show a tendency to spatter when painting with a roller.
In order to meet these requirements, paint manufacturers test various formulations with regological additives to minimize and eliminate this problem. Splashes are usually eliminated by using special types of cellulose ethers and HEUR rheology additives. Typically, however, paint spattering tests are conducted by inviting a paint team and testing different samples applied by them with different rollers.
Of course, such tests are needed, especially when we want to test the behavior of paints in relation to different rollers and the skills of different painters. However, when we talk about the early stage of laboratory formulation work, such tests do not make much sense. What is needed is a method that will allow, regardless of the type of roller or the painter’s skills, an absolute and objective assessment in the laboratory. Sometimes rheological tests on rotational rheometers can provide some data on paint behavior in the high shear region and translate these results into paint roller coating behavior, however, it is not a method that provides a reliable correlation between viscosity and spattering tendency.
ASTM D4707 “Standard Test Method for Measuring Paint Spatter Resistance During Roller Application” test method was developed for this purpose. t consists in causing the paint to splatter applied to a black normalized panel with a notched spool test roller at a certain sequence of movements and speed. Spatter caused by cuts on the roller are trapped on the underside of the sheet, and the ink splatter dot pattern is assessed with the ASTM D4707 photo standards.
The coating is applied with an automatic drawdown machine using a standard gap and the test is performed immediately after application to the wet coating. The speed of the roller is relative to the metronome and is 80 bpm. This method requires very good coordination skills from the operator and practice to ensure proper roller guidance (constant contact of the roller surface with the coating is required) and to ensure the accuracy of the test (0.5 units of the splash scale for reproducibility). To increase precision, it is of course recommended to participate in the ILC and use reference paints with known spattering tendency values according to ASTM D4707.
As a result, results are obtained on a scale from 0 to 10, which are readings from the standard scale, and intermediate grades that should be interpreted on the basis of intermediate scales. Below are two samples rated 7 and 3 according to ASTM D4707 and refer to different rheological additives (samples from the Spektrochem laboratory).
The ASTM D4707 test method has been used in the Spektrochem laboratory for many years to test rheological additives and test paints for spattering tendency during roller application. Its introduction required many inter-laboratory tests, however, refined at the current level, it is an excellent tool for laboratory tests without the need to involve painters to perform tests. The method provides objective, fully repeatable and reproducible test results for evaluation of interior and exterior latex paints.