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Ask the Expert Question-and-Answer Archive

by Ron Joseph

June, 2005

Converting a DuPont Number to a RAL Number

Q. Is there a way to convert a North American paint code to a European code? I have a DuPont # N0216EA but my European supplier only understands RAL#'s.

A. Your question was referred to me by Mr. Ron Joseph.

From your email address I deduced that your company is in the large crane business. Paints finishes for these machines are usually not of the "metallic" type; however, if this is the case, then a more elaborate specification is required.

First, I would recommend checking if your supplier requires a RAL Classic or RAL Design number. RAL Classic is limited to 210 colors and the chances of finding an equivalent to your color are slim. In the likely case that he accepts RAL Design numbers, your color could be translated to this system. In the more common cases, two or three RAL Design patches around your sample color would be specified.

Here are a few methods to find an equivalent:

1- If your supplier has some dedicated intrumentation to analyse color samples and build color recipes, send a painted sample, preferably flat, to your supplier, and ask for a match.

2- You could purchase RAL Design patches and visually try to match them to your sample. This method requires that attention be put in the lighting environment used for comparison. I suggest using the light under which the finished product will be seen, in this case daylight. A calibrated light booth is ideal for this task, but light from a window, around noon, not direct sunlight, with room lights closed, and a room with neutral (ideally gray) colored walls, floor and ceiling, should do. Be aware that the color patches may not be manufactured with the same pigments as your paint and that if they match under one light, they may not under another. You could ask the same from your supplier, but he may not want to be the judge for this match.

In North America, RAL patches can be purchased from Dorn Color Inc.

3- Using dedicated instrumentation and software, measure the RAL equivalent of your sample. I understand that this solution is not trivial but it can be performed by consultants, such as myself. Then send the numbers, plus a sample, to your supplier. By sending the sample, he will also have an idea of the finish.

In all cases, ask your supplier to return a painted sample which you will compare to your original, for approval (the comments on lighting given above also apply here). If critical, a color difference (DeltaE*ab or other formula) should be specified to prevent any misunderstanding. Alternately, the tolerance could be given in terms of RAL Design numbers.

If you are interested, I could measure the equivalent RAL design number of your sample. I can send you a quote on request.

Best regards,

Danny Pascale

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