Does plexiglass (like you get at homedepot or lowes) block UV rays? I may need to use some for humidity control but dont want to block out the UV.
Plexiglass filters out most UV rays smaller than 300nm (some Plexiglass is treated to filter all the way to 400nm), UVB rays range from 280nm to 315nm. According to the info that ZooMed has out on their ReptiSun 5.0 bulbs (both linear and compact) the output of UVB from them ranges from 300nm to 320nm.
What this means is theoretically Plexiglass (as long as it wasn't treated to filter the longer wave lengths) should not affect the waves much. The only way to know for sure is to use a UV Meter, unfortunately I don't have any Plexiglass laying around to test this at the moment.
I got out my meter
first checked a cage at 10 inches down with screen top metered at 38
Next checked a cage at 10 inches down no top but optix brand of plexiglass metered at 0
Next checked a cage at 10 inches down no top but lexan brand of plexiglass metered at 0
So I would say uvb DOES NOT go thought plexiglass
When reading below, keep in mind "Plexiglass" is just one of many brand names for a material called acrylic.
Found this online (from the manufacturer):
>>>"OPTIX clear acrylic sheet has UV transmittance of 10-20% (in the 250-400 nm wavelength range), and visible light transmittance of 92%."<<<
However, almost ALL of the UV below 360/370nm is filtered out, which would confirm Laurie's findings - normal clear acrylic will filter out pretty much all of the UV produced by our UVB bulbs(typically 300-320nm). The only acrylic material that will allow more UV through is a special UV transmitting acrylic. This is the type of acrylic used in tanning beds and it allows most of the UVB spectrum through (down to about 280nm), but this is not the acrylic which is usually offered for sale. This information is consistent for both "Optix" brand and "Plexiglass" brand acrylic sheets.
Just a note - Lexan is not plexiglass or acrylic - it is a brand name for a material called polycarbonate - much different than acrylic - not as clear and scratches much more easily, but it is much more impact resistant.