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SPF - Questions
How well do the SPF-290S results correlate with in-vivo results?Our long experience and customer feedback indicates that the SPF-290S results correlate extremely well with in-vivo results. Several customers provided actual sample data which is presented in graphical format in our brochure on the support page.

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Can the SPF-290S results be used instead of in-vivo testing?For final results, not yet, according to the U.S. Food and Drug Administration. However, because of the extremely good correlation with in-vivo testing results, the SPF-290S can be an enormous time and cost saver during the the product development and formulation stages.

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Why is the wavelength range from 290 NM to 400 NM? According to the US Food and Drug Administration's monograph (Federal Register, Vol. 64, #98, FDA 21 CFR, Parts 310, 352, 700 and 740), as well as industry-recognized computational standards (see the Diffey/Robson technical presentation, "A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum" in the J. Soc. Cosmet. Chem., 40, 127 ‚ 133, (May/June 1989)), SPF's are calculated on the basis of measurements taken in this specific wavelength range.

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Why does Optometrics' SPF-290S use a continuous UV source instead of a flash lamp? Because a continuous source is required by the US Food and Drug Administration for in-vivo testing and the SPF-290S was designed to simulate in-vivo testing as closely as possible. This is further confirmed by referring to the Diffey/Robson technical presentation, "A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum" in the J. Soc. Cosmet. Chem., 40, 127 ‚ 133, (May/June 1989), which states that "the principle of the present method is to measure the spectral transmission of ultraviolet radiation through a sample of Transpore tape with and without the sunscreen applied. Any radiation source may be used, providing there is a continuous spectral power distribution between 290 and 400 NM" (emphasis supplied).

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Can I export the SPF data to my spreadsheet or database? Of course you can. The SPF data is stored in standard ASCII format, easily recognizable and readable by all well known and popular spreadsheet and database programs, e.g. Excel, Lotus 1-2-3, Access, etc.

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How do I spread samples? Briefly, a substrate such as Transpore tape, VitroSkin, quartz plates or other suitable UV-transmitting media, is laid across a sample holder. A reference scan without the sunscreen applied is taken. The sunscreen cream, lotion, cosmetic is applied in small dabs or spots over an area of 40+ cm. Square and then spread evenly (manually, using finger cots) to achieve a uniform thickness of 2 ml/cm2, as required for in-vivo testing. A more detailed explanation can be found in both the WinSPF software manual and in the WinSPF's on-line help system.

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Does the SPF-290S produce measurable Ozone?Many electronic devices produce Ozone, even in trace amounts. The ozone produced by the instrument does not appear to be within the sensitivity of any test method of which we are aware; this conclusion is based on testing performed by ILC Technology, Inc., producer of the LX150UV light source [Engineering Note 224, prepared in 1995].

We have tested this by purchasing safety badges and strips that detect ozone. We purchase them from Lab Safety Supply (www.labsafety.com) part numbers 1A-5155-6 and 1A-5154-6. Our personnel have used the badges sitting next to the SPF unit and running it for several hours at a time and the badges indicated no ozone detection. Lab Safety claims that the badges and strips are sensitive to 0.1 parts/million in a fifteen minute span so they should be extremely sensitive.

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What is the Star Rating based on? The star rating is based on the average UVA/UVB ratio. A different rating is given to a range of values as shown below.
 
UVA/UVB Ratio Star Rating
<= 0.199 0
0.200 to 0.399 1
0.400 to 0.599 2
0.600 to 0.799 3
>=0.800 4

 

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