Certain guidelines should be followed depending on the type of bulb being used. Because tungsten filament bulbs burn continuously and generate a considerable amount of heat, heat and light sensitive samples should not be placed at the instrument port until immediately prior to measurement of the sample. Extended exposure of some samples to the heat and light from the tungsten filament bulb will cause a dramatic change in the color of the sample. Xenon flash bulbs do not generate heat, but they are very rich in ultraviolet energy. This ultraviolet energy will excite any fluorescing chemicals, additives, or dyes present in the samples and will lead to inaccurate match predictions, especially in the blue area of the visible spectrum.
Filters are usually available to minimize the effect of ultraviolet energy.
All samples should be measured multiple times with the largest area view available on the spectrophotometer being used. A repeatable measurement technique based on the number of layers of material used and sample rotation should be developed prior to measuring the primaries. Two to four layers will be sufficient for most knitted and woven materials to achieve an opaque sample for presentation to the instrument. Lightweight and translucent materials will often require so many layers to become opaque that the material is forced into the interior of the instrument when measuring, causing inaccurate measurement. For these types of materials, repeatable results can be obtained by measuring only a few layers of material backed with a white ceramic tile similar to the instrument's calibration tile.