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Polythene gauge for winter protection

CollareddoveCollareddove Posts: 173
in Tools and techniques
I am wanting to create a small version of a polytunnel/cloche to protect some autumn/winter salad leaves etc.  My existing polytunnel has 200 micron gauge polythene. Looking online for a similar or slightly thinner gauge (for easier flexibility) all the polythene seems to be graded as 'gsm' which, l understand does not relate to microns. I'd like some advise as to what gsm l should go for?  There seems to be a complicated formula to work this out, which l cannot begin to understand!

Posts

  • FairygirlFairygirl Posts: 55,117
    Not something I know about @lesleymeyrick, but lots of folk on the forum will use various polythenes for different reasons, and might be able to help. 
    My reply will, at least, bump your query up the page :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • JennyJJennyJ Posts: 10,576
    This web page explains it in a not-too-complicated way, and gives a formula using an average specific density for polypropylene roofing sheeting (down near the bottom). Only thing is, I don't know how similar that is to the plastics that you're looking at for the polytunnel. I think I'd just go to a DIY place, look at/feel what they'd got, and make a judgement.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • CollareddoveCollareddove Posts: 173
    Which web page please? Nothing showing.
  • JennyJJennyJ Posts: 10,576
    Oops, don't know what became of the link. Here you go https://www.tarcoroofing.com/blog/320-thickness-versus-gsm
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • CollareddoveCollareddove Posts: 173
    Thank you, a bit of bedtime reading!
  • CollareddoveCollareddove Posts: 173
    It seems that although not exact, for my purposes 1:1 will be ok, microns being 'a bit' thicker than gsm, but not enough difference to matter to me.  Thanks for the link!
  • FairygirlFairygirl Posts: 55,117
    Glad you got some help @lesleymeyrick.
    She's quite good - that @JennyJ ;)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • JennyJJennyJ Posts: 10,576
    Aw shucks @Fairygirl :blush:
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • FairygirlFairygirl Posts: 55,117
     :D 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
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