Getting the best out of your laboratory weathering testing depends majorly on three questions:
- Which is the most suitable weathering device for my product?
- Which is the best test method I can apply?
- What is the ideal test setup / specimen preparation?
Especially the third point, "How should I prepare my test specimens?" is a frequently asked question. The following comments will provide you with first general insights and practical advice on how to get specimen preparation right for weathering testing.
General Guidance
ISO 4892-2 on xenon weathering of plastics states:
"...Specimen holders may be in the form of an open frame, leaving the backs of the specimens exposed, or they may provide the specimens with a solid backing".
And further, "...the backing might affect the results..., particularly with transparent specimens".
The American standard ASTM G155, a general guidance for xenon weathering, provides similar insights for the use of a backing sheet inside the specimen holder:
"Any backing used may affect test results and shall be agreed upon in advance between the interested parties."
Practical Advice
Referring to these insights, here is my advice for when to use backing and when not:
- Do not use a backing when you prepare transparent specimens as the backing made of stainless steel or aluminium will directly reflect UV radiation and pass through the sample a second time. Bad correlation to natural aging can be the consequence.
- Whenever preparing lose or very thin specimens such as textiles, leather, or foils, then use a white cardboard to provide fixation and proper alignment. However, only use bleach-free cardboard, as such chemical vapor from the cardboard may affect the exposure.
- Do use the stainless-steel backing coming with our holders when you prepare opaque specimens such as dyed or coated polymers. The backing sheet protects against any potential influence from behind and weathering solely occurs on the exposed front.
Specimen preparations for Atlas Xenotest: a) with closed backing, b) with open backing, c) on bleach-free cardboard
More Information
For guidance on weathering and lightfastness testing, contact us, have a look at our technical library, review upcoming educational events or learn more about instrument technology.
Listen to recorded webinars on xenon-arc weathering instruments, the difference between xenon and Fl/UV devices, or setup of common laboratory weathering tests.