Safe plastics that can be used for soil covers? One to avoid? Looking at options for SIP 'shower caps'

So last time I just used trash bags and a big ass rubber band to make my 'shower cap' for the SIPs I ran. I'm looking for something different this time & was looking at the shelving/drawer liners and I see they sometimes say "pvc-free" or allude to not being food safe (touching it directly) so that got me to thinking about which types of plastics to specifically look for and which ones to specifically avoid.

I was looking also at the vinyl floor runners & the likes as they're nice & heavy/opaque but I'm sure those aren't likely going to be 'food safe' given their intended uses.

Also, with simply touching the top of the soil - potentially in contact with a fungal mat (myco) - do I really need to be that worried about it? I've looked at a few options online and there'r the usual bands like Gorilla Grip, Contakt, etc.

My main criteria is opaque & helps prevent transpiration of soil/medium as well as allowing me to rig my watering apparatus underneath so I can top-feed as desired. If the color is white, super as that'll help reflect to the under canopy. I figure there's paths out there I've not thought of so hoping someone has some suggestions aside from the obvious ones. I know in some food industry or skilled trade/industries they've got to use something that might be applicable here.

What are you trying to achieve?
Other than complicate simple soil growing?

If you look at the Earthboxes and other SIP based designs, they usually have a plastic cover. Helps with moisture control and wicking, etc. Also helps control humidity in the grow environment. I was trying to get my nice fuzzy white mat growing as well when I top-dressed so again if you look at SIP(s) most people running them use a cover which helps foster that.

And I wouldn't call it complicate... it's achieving optimal environmental conditions both for the medium & the atmosphere.

NewGrower2011 said:

If you look at the Earthboxes and other SIP based designs, they usually have a plastic cover. Helps with moisture control and wicking, etc. Also helps control humidity in the grow environment. I was trying to get my nice fuzzy white mat growing as well when I top-dressed so again if you look at SIP(s) most people running them use a cover which helps foster that.

And I wouldn't call it complicate... it's achieving optimal environmental conditions both for the medium & the atmosphere.

Click to expand...

What about a mulch or cover crop or are you trying to go for the mycelium mat below cap? I built my own sip pots and unfortunately did not think of the type of plastic I used do you know of any information on the effects?

Not sure on ill-effects of various plastic types. I'm doing a quasi-coco run this time so hadn't went the cover-crop path quite yet in my adventures. It might be the next run though.

As I do intend to top-feed synth nutes (Botanicare KIND which I need to use up) and didn't build a true super soil this time I need to have easy enough access to the medium. That or get off my ass and get that automated drip setup going I keep skipping and just leave it under the cover. I've built part of my manifold but need to revisit that in 'next time'...

Last time I just threw heavy duty black trashbags on top/between stems & the fill/air tube and used big ass rubber bands to secure them. Was just hoping to come up with something a little better this time. It did work...

I'm pretty sure the commercial ones are just garden cloth (the kind that blocks light for weed control). It breathes but doesn't let much light through. You can find it at any garden center.

I don't bother with it anymore. Just pull a few weeds if growing outdoors. Indoors, I haven't had any issues going naked. Even the growkashi still forms a nice matt of mycilium (sp?) if I put a thin layer of topdress on like earthworm castings.

Also for anyone curious, even without the cap/cover my drench with activated EM1 seems to have taken ahold. The surface drying out just means it's not as prominent as when I had done the same before with the bag coverings. I top-dressed with fresh ground malted barley and the other amendments and laid the EM1 on a little on the heavy side.

I used Mykos/Azos on 2 of the 4 and they all got EM1.

Last time I used some 'Kashi Blend' from BuildASoil and it looked to be a strong strain they are using or something else it contributes as it really took hold. I've meant to order more but have held off until warmer weather. With this covid shit who know how long shipping would happen, if it happens...

You want to use an addition polymer (polyethylene or polypropylene) or a rubber. Personally, if I was using SIP I would get high quality pond liner, NOT PVC liner. The one I have to hold my bedrock is basically a rubber polyethylene mix, which is super strong and wont leach any undesirables. I don't know the name off the top of my head. Call you local pond store and ask for non PVC pond liner, they should have it if they are worth anything. When you go to buy, you'll be able to tell if it is rubber.

Good point, especially the ones for Koi ponds etc which would have to be the safer variant. That's the type of input I was looking for. Thanks!

I imagine I can find this in either the general pond retailers or perhaps those handling aquatics/aquarium supplies. Time to go hunting as I'm starting to see the humidity climbing with things getting warmer and more biomass/frequent feedings. Covering the medium will hopefully prevent a lot of that climb before it becomes an issue in flowering.