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Construction Physics

MasterLynxx

New Member
Does Glass Paneling help with illumination?

Should mylar be placed behind translucent 4 mil. plastic to increase humidity moisture?

How can I determine how much weight tempered glass can withstand?
 

HiTech-Hate

New Member
NOTE: Before you read this, you said 'physics', so most of what I say is basic physics, not trying to sound arrogant nerdy, blah blah, just trying to explain the physics :)

1. I don't know what application of glass paneling your speaking of, but the refractive index of glass is about 1.5 (not gonna nitpick because it is slightly different for each wavelength of light).

The two implications of refraction from air through a medium (glass) as it applies to you are the angle of refraction, and the amount of light reflected back into the medium (glass).

Angle of refraction refers to the change in angle of the light coming out of the glass due to refraction. Light entering the glass at some angle (lets say head on, so 90 degrees) from air (which has refractive index 1.0) will be refracted in the glass (refractive index 1.5) and its angle will change according to Snell's Law:

N(air) * sin(air) = N(glass) * sing(glass)

N(air) = refractive index of air, N(glass) refrac index of glass, sin(air) = angle the light hits the glass coming from air, sin(glass) is the refracted angle, the number we want !

Assuming the 90 degree incident angle

(1.0) * sin(90) = (1.5) * sin(glass)
o.6666 = sin(glass)
glass = 42 degrees

So glass does have a fairly significant change on which direction the light will be traveling when it leave the glass compared to when it entered the glass, and you'd prolly want to take this into account when inserting these glass plates, as to the angle you put them in with regards to the lamps emitted light.

ALSO, the glass will reflect a certain amount of light entering it, as described by this equation:

R = [(nair-nglass)/(nair+nglass)]^2
R = [(1.0-1.5)/(1.0+1.5)]^2
R = 0.04

Which is 4% obviously

I personally don't see any reason why you would want to put glass panelling in at all, as for one it will reduce the amount of light that gets through 4% isn't a lot, but not using glass paneling at all and just keeping that 4% is better. It also mucks with the direction your light is taking to get to your plants :p

2.I don't know how mylar behind plastic would increase humidity, can you source me to the scientific principle or research and I will look? I don't think you want that kind of passive humidity added anyways, you usually want to keep humidity down, and if it needs to be increased at all, can be done so by a $15 very small cool or warm mist humidifier (and the warm mist will help with temps as well if they are getting low say at lights off), which u also have control over, opposed to the passive mylar/poly.

3. I don't know, and i'm not sure why anyone would want to put heavy things on glass in a grow room, but again I don't know your setup

Sorry if this was long-winded, and sounded like I just wiki it all. I DID NOT lol, i'm a scientist, basic principles, thats why I just took all that time to make this response, to get some succinct and accurate info out there :) (not to say there isn't plenty already, you just gotta sift for it)
 

MasterLynxx

New Member
Well the scientific rhetoric did have me a little twisted, but all in all I followed ya. I was wondering out of curiosity. I do know greenhouses are made from glass, and used the paneling I have, which is tempered btw, as shelving for additional planters. I plan on utilizing the plastic sheeting, because when I mist my plants the moisture stays on the mylar and spot stains. So for sanitary purposes, as well as retaining the humidity in the closet. The closet is a hand made 2'x3'x6' wood framed cabinet.
I am using CFL & LED's for lighting. The lights and the glass are I'm hoping best angled for light magnification... I will send a pic, in PM, but it is still unfinished, so does not have all of the discussed materials in yet. I just finished putting in the shelves.
NOTE: Before you read this, you said 'physics', so most of what I say is basic physics, not trying to sound arrogant nerdy, blah blah, just trying to explain the physics :)
Smoke 14u bro, thank u...
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
Should mylar be placed behind translucent 4 mil. plastic to increase humidity moisture?
Isn't plastic waterproof?

light magnification
Huh?

I've seen glass floors in old buildings - but it was probably really thick. Glass is stronger than many people think, for all that it's kind of a liquid. You can place a 16 pound bowling ball on a drinking glass. I think it's more the sharp impact than the actual weight that breaks most glass.

I've heard of tempered glass just shattering in patio tables. A friend had a set of glass shower doors for years, no problem. She was in her bedroom one day reading and heard one go (there was no one else in the house). I guess you never can tell.

I dropped a piece of ¼" one day and neither it nor the concrete floor were harmed. But I was probably lucky.

A .50 caliber AP round will go right through five pieces of ½" and still have enough energy remaining to then go through the car door that the glass is against, lol.
 

HiTech-Hate

New Member
I do know greenhouses are made from glass, and used the paneling I have, which is tempered btw, as shelving for additional planters.
Well greenhouses are structures designed with sunlight being the primary light source. I would think the tempered glass is a structural decision, with walls many feet high and many feet long.

You said the structure you are growing in is a "2'x3'x6' wood framed cabinet", so clearly you are not building a greenhouse (and presumably your light source will be internal, opposed to a greenhouse), so I regress to my previous confusion over why you are using tempered glass at all?
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
Having accidentally attempted to walk through untempered glass - and bleeding profusely - I could understand the wish to use tempered glass indoors. Especially if the person doing so might occasionally walk around the premises after having consumed a quantity of cannabis. Not that it makes us stupid; in fact I've been known to contemplate many things after having consumed - just often not what was directly in front of me, lol.
 
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