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Determination of Wet Edge TimeBS 3900-C1 |
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Scope and Field of Application
A correctly formulated air-drying paint begins to dry as soon as it is applied to a surface. It is possible to formulate paints with a wide range of drying times but the actual choice is always a matter of compromise.
If the paint dries too slowly then this delays the application of any subsequent coats and also prolongs the time that the coating can be marred or can accumulate dust particles.
A short drying period also has disadvantages. If paint is applied to large areas then it is important to be able to blend in freshly applied paint with areas where the paint was applied several minutes earlier. If the paint applied earlier has already dried, the edge between it and the freshly applied paint will remain visible and the overall appearance of the surface will be patchy.
BS 3900-C1 is a method of measuring how long a paint remains workable after it has been applied.
There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.
The actual standard is a copyright-protected document and we are not able to provide you with copies. If required however, you can easily obtain copies from the British Standards Institution.
Summary of Method
The method involves applying the test paint to a 600 x 300 mm burnished steel test panel. The panel can be primed or undercoated as required. Half the panel is coated and then left for an agreed time. The remaining half of the panel is then coated, starting at the edge of the surface already painted.
Once the paint has dried, the surface is examined to see if the join between the two paint applications is visible and if there is any evidence of lack of levelling or variation in colour.
Sample Requirements
We require 1 litre of coating.
Accreditation
PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.
Please contact Peter Collins for further details.
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