Brightness measurement and surface finish correlation
Our company produces equipment for the Bio-Pharm industries which is very sensitive to surface finishes. Our product is machined, mechanically polished and in some cases electropolished to achieve specified surface finishes. Our products have complex shapes that are sometimes difficult to use traditional profilometer type measurement.
The quantitative measure of brightness or shine has been discussed as a possible quality measurement. Is there a technology to quantitatively measure brightness or shine, and also can these measurements indicate other surface characteristics?Paul McClune
- Lancaster, Pennsylvania
I don't have a direct answer to your question about reflectivity versus surface finish. I would like to let you know that there are other methods for evaluation of surface finish that may work better on complex parts than surface profilometry. There are non-contact optical measurement methods that can account for irregular shapes to give very accurate surface measurements. We have also used surface replicas to obtain samples for surface roughness evaluation on internal surfaces and other inaccessible locations.
Brightness or whiteness can be measured with a glossmeter, that measures, if I'm not wrong, the reflectance of light at different angles.Calibration is made on a white glossy enamel and, on the other side, on black paper. There are many companies producing glossmeters. Of course brightness is the reverse measure of mat-ness.
- Sulmona, Italy
There is a company in Texas (Graphics Arts Manufacturing company) who makes a Reflectance Densitometer that is the standard technique to measure the brightness of silver plated surfaces in the electronics industry. Silver readings of 0.4 or less are called matte, 0.4 to 1.1 are semi-bright and higher readings are called bright. Hopes this helps.
St Paul, Minnesota
REFLECTIVITY AND SMOOTHNESS
YOU ARE STANDING ON A DOCK LOOKING AT A REFLECTION OF THE SUN. WHICH SURFACE WILL SHOW MORE LIGHT, THE SMOOTH OR THE ROUGH WAVELETS?
I CONTEND (WITH NO PROOF) THAT LIGHT REFLECTION CAN BE VERY MISLEADING AS A GAGE OF MACHINING SMOOTHNESS. REFLECTIVITY IS A PROPERTY OF THE SURFACE AT THE MICRO LEVEL - BELOW THE MARKS MADE BY MACHINING. IT CAN BE A GAUGE OF FINE GRINDING AND POLISHING OPERATIONS BUT NOT OF MACHINING.
I'M A VETERAN TOOL MAKER AND TEACHER OF MACHINING. I CAN'T SAY EXACTLY WHEN I TOOK THIS TO BE TRUTH BUT IT'S BEEN WITH ME MOST OF MY 30+ YEAR CAREER. AM I WRONG?MIKE FITZPATRICK
- ARLINGTON, Washington
An interesting topic! My interest is in the determination of all (measurable) aspects of a plated parabolic reflector which account for the highest reflectivity. Our parts are vacuum metallized with aluminum with an added clearcoat for protection.
Aside from physical dimensions, how can I measure the "polish" or surface finish and correlate to (ultimately) a functional test for lumens, candlepower or "brightness"? Will a simple glossmeter (used in the powder coating industry) give any useful measurement?Rick Gallagher
- Kempton, Pennsylvania
July 25, 2012
Q. Dear Sir,
Our customer did a study and found that Dr. Lange >46% was similar to >1.0 Gam (Ni and NiNiP plating). However we are using Gam densitometer to measure the Ni & NiNip brightness.
Do you have any reference for Gam vs. Dr. Lange, or conversion table for our reference?
- Malacca, Malaysia
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