Frosted glass for a cold frame - any use?

[organic]

Hey folks - a house over the road is having some work done and they've just skipped a door with a single, full length obscure glass pane in it. The glass is still intact. There are a few coloured bits but on the whole it's colourless, but obscure glass.

I'm thinking about taking it out and using it to make a cold frame (making the 4 sides from some salvaged wood I've got and hinge the door from one edge) for my allotment.

It's got me wondering though - is obscure glass going to be a problem? I can always use it for now and swap it for clear glass the first chance I get - but if it's really not worth it I won't bother at all. I expect slightly less light would get through, and it'd certainly be more diffuse than light through normal glass would be, but beyond that I don't have a clue.

So - use it or forget it?

[Snadger]

Use it! If its got a coloured glass panel in it you'll have the poshest cold frame in town!

[Patchninja]

After all, those polycarbonate greenhouses aren't transparent like glass either!

[sarraceniac]

See the post on 'Light boxes' in the technical bit. Use it.

[organic]

Thanks for the replies folks.

Snadger - It will look quite posh, I think.
I'm throwing together a quick sketch of the frame in AutoCAD now - even though I don't have the actual measurements of the door yet. If nothing else it will be a good start.

Patchninja - That's a good point about the polycarbonate ones. I hadn't considered that.

Sarraceniac - I get the feeling that's more to do with my other thread about coloured bulbs (and is certainly a good read - I'll be putting that really helpful info to use - cheers) - or does that apply to cold frames too? If so I don't think I'm too sure how. (This is all very new to me y'see.)

[SarzWix]

The only thing you should be careful of is if there are any 'bobbly' bits of glass in the pattern - my friend's best windowsill for light purposes is the bathroom one, but, some of the bobbles in the glass act as a lens/magnifier causing burn spots on the plant leaves I should think it's easily solvable though, by painting a dab of shade paint/whitewash or similar onto any suspicious bobbles

[organic]

Food for thought.
I'll inspect it (and suspect it might be ALL like that).

[sarraceniac]

Whether you use the sun or some form of artificial lighting is irrelevant to the plants Organic. What matters is the wave length and the intensity of the light. If the sun on a bright day (remember those?) is 20,000 lux and a plant only requires 2,000 lux then you can afford to lose 90% of the light on a bright sunny day and probably 70% on a cloudy day without starving your plants. Even if the glass in the door is stained green, even though it will filter out much of the rest of the spectrum which is useful to your plants, it will still transmit enough light around the red and blue wavelengths to keep the plant happy. Thus the semi-technical bits of the light-boxes posting are relevant.

Sarz' cautionary story is good. However, as long as your frame (i.e. light box) is deep enough so the glass is well above the plants, you should have no problem. You can get translucent glass paints however. You would need very little (a couple of squid) and as you can see from this,

WikiAnswers - What color of light do plants grow best in

if you can get or mix a purplish colour then so much the better. I'd try it plain to start and if you see leaf burn then dab on some translucent paint.

[organic]

Ah of course, I see the relevance now! I don't know why, but it hadn't occurred to me that there was such an abundance of light that I could afford to lose so much and still have healthy plants in the frame.

As for bright sunny days... Easter Sunday made a really good effort. There were spots of cloud and the odd nippy breeze, but for the most part I was wearing a teeshirt and being warmed by the sun as I dug. Not bad for this time of year.

I'll be grabbing the door tomorrow morning and hopefully making the frame up at some point this week or next weekend. I'll be sure to bore everyone with the details and pictures when it's done.