ID Help for Mini Cacti and a couple of other questions.

[KittieKAT]

And if u get really sunny sunny days make sure u let ur cacti get adapted to the change in light strength before opening the shades just yet cause they can burn pretty bad without giving it time to adjust to the changes in lights, i kno that because some mean guy ripped off my winter sun blockers on my Windows And killed most of my collection and burned many of the rest and some got frost damage aswell... but I'm not gonna get into that again grrrr... Goodluck!

[greenknight]

This is the North of England we're talking about, quite a bit farther North where the sun is less intense, and an East-facing window to boot. Can't hurt to take it gradually anyway, but I don't think the risk of sunburn is very high.

[Mooly]

Around 55 degrees north here but its surprising how hot the sun can be through glass even at this time year. Another few weeks and things really will start hotting up.

[DaveW]

Yes plants can also burn behind glass in a greenhouse with prolonged exposure where they would be OK in sun outside, usually due to better air circulation outdoors cooling them. Plants also cannot move when they are getting too warm:-

"Ordinary glass absorbs 97 per cent of the UVB rays that cause sunburn and some skin cancers, and 37 per cent of the less harmful UVA radiation. This translates to a protection of about SPF30, so you can still get burned with long enough exposure. Car windscreens have a plastic layer bonded between two layers of glass and this blocks all the UVB and 80 per cent of the UVA, making sunburn very unlikely."

[Mooly]

Thanks Dave. I'd never given much thought to the properties of glass re uva and uvb. No chance of sunburn today. Cold overcast and foggy mostly.