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Optical Coatings & Materials FAQ

Frequently Asked Questions

What is the Typical Thickness of Spectraflect or 6080 Coating?

Labsphere's Spectraflect and 6080 diffuse reflectance coatings are applied by spray painting onto a specially prepared surface. The coating is built up gradually in layers and the optimum thickness (that which gives the specified reflectance) is approximately 0.5mm.

Can I Purchase Spectraflect Coating?

Not exactly. Spectraflect is the name we give to the standard diffuse reflectance coating that we apply at the factory. If you want to paint your own reflectors with a barium sulphate-based formulation, Labsphere's 6080 coating is available.

Can I Purchase Duraflect Coating?

No. Duraflect is our waterproof diffuse reflectance coating and this is only available as a coating service.

Why do you Recommend that I Apply 6080 Coating by Spraying?

The raison d'être of 6080 coating is to provide a uniform, diffuse surface of high reflectance. This is accomplished by gradually building up the thickness of the coating in separate layers to about 0.5mm. For repairing localised damage to an integrating sphere coating, brush painting of 6080 is practical. However, for larger areas, brush painting is not viable. As you seek to apply new layers, the solvent used in 6080 (ethanol) will dissolve the underlying layers which will result in a very poor quality finish. Spray painting is strongly recommended.

Can I Clean an Object that is Coated with Spectraflect?

Not easily. Light soiling of a Spectraflect coated reflector can only be accomplished using an air brush. Heavy soiling will probably necessitate that the object is recoated. Spectraflect (and 6080) is a hydroscopic material and if you try to clean the reflector in water, you will simply dissolve the coating. Avoid. 

What is the Advantage of a Diffuse Reflectance Surface?

Our diffuse reflectance materials and coatings are used in a number of applications, but all exploit the fundamental property that the radiance of light reflected from a diffuse reflectance material is constant with all angles of view. By definition, a perfect diffuser will obey Lambert's cosine law that states that the radiant intensity (flux per unit solid angle) will vary with the cosine of the angle subtended between the direction of view and the normal to the surface. Also by definition, if the intensity varies with the cosine of the angle, the radiance (flux per unit area per unit solid angle) will remain constant. Thus, a Spectralon diffuse reflectance standard will provide a stable reference of reflectance that does not vary with illumination or viewing geometry. In other words, your measurements will be much more reproducible compared to the case of a glossy (specular) reference.

Are there Guidelines for Submitting A Drawing for a Spectralon Reflector?

We are happy to assist with your design requirements for fabricated Spectralon components but submitting your own mechanical drawings will help reduce the time and costs associated with your product development. Ideally, submit your drawing electronically in one of the following formats: Solidworks; AutoCAD; Microsoft Visio; IGES, SAT, DXF, PDF or BMP formats. Your drawing should clearly state your part number, reflectance value required, dimensions, tolerances, any special machining instructions and both first and third angle projections if possible. Apart from the size and complexity of the design, the major cost drivers are requirements for calibration or witness plates, any special tooling, and tapped holes or threaded inserts. Please note that our standard machining tolerance is ± 0.13mm.

Can I Purchase Bulk Spectralon?

Unfortunately, no. Spectralon is a soft thermoplastic that requires specialist machining in a very clean (oil free) environment. We offer a prompt and cost-effective reflector fabrication service that will provide components to your exact specifications with the quality guaranteed.

Why do you Recommend a Minimum of 7mm Thickness for Spectralon?

Spectralon achieves its high reflectance as a result of bulk rather than surface scattering. Experiments have determined that the reflectance of Spectralon is maximised for thicknesses of 7mm or higher. We therefore recommend that your reflector possess a minimum wall thickness of 7mm if you are to exploit the high reflectance of Spectralon. However, Spectralon can be machined in thinner section with reduced reflectance. For example, the reflectance of optical grade Spectralon is 99.0% at 550nm at the optimum 7mm thickness, but this drops to 98.9% at 5mm, 97.2% at 3mm and 93.3% at 1mm thickness. Where thin sections are unavoidable (due to space constraints), we can in certain instances dope Spectralon with barium sulphate to partially restore the lost reflectance. Taking 1mm thick Spectralon as an example, undoped material will have a reflectance of 93.3% at 550nm, whereas doped Spectralon will give 95.5%. For further information, please refer to the Technical Guide to Materials & Coatings which you can download from the documentation page.

Can I Really Clean Spectralon by Sanding?

Yes. Light cleaning of Spectralon is best done using compressed air (please do not use Freon). For heavier soiling, use fine wet-and-dry paper (220-240 grit) to "sand" the reflector surface under running water. You will know that the surface is clean when it becomes hydrophobic (i.e. the water beads up). For full instructions, consult the Spectralon care guidelines which you can download from the documentation page. This method of cleaning Spectralon by resurfacing under light sanding applies just as well to Spectralon reflectance standards. Consider that Spectralon is a bulk (not a surface) reflector, therefore removal of a thin layer of material on the surface of the Spectralon does not alter the bulk reflectance properties of the standard. Obviously, you can only sand the surface so many times before you run out of material, so the best practice is to handle the Spectralon standards with care, as is normal with calibrated artifacts.

What Substrates can Infragold be Applied to?

Infragold is Labsphere's electro-plated, diffuse gold coating used for reflectance applications in the near to mid infrared spectral band. In general, Infragold can be applied to aluminium, nickel, copper and steel. 

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