Foil VS Mylar - truth or accepted on faith?

[PlanetJ]

Ã'm adapting this question from a different forum, where I stumbled upon a thread about this issue.

The starting post of the thread goes like this:

Starting post:
khronik
Mylar vs. foil

For a long time I assumed everyone knew what they were talking about when they said not to use aluminum foil, and to use mylar. Apparently foil can create hot spots. But here's the thing, so can mylar. In fact, it's often used precisely because of its ability to reflect heat!

Anyway, I've heard all sorts of misinformation, like that aluminum foil is only 40% reflective whereas mylar is 98% reflective. So I looked up some data in my thermodynamics textbook from college. Actually, polished aluminum is MORE reflective than mylar! Most mylar has a bit of transparency to it, whereas aluminum is completely opaque. And here's the kicker: mylar is made reflective by depositing aluminum on it!

Aluminum is used because it has a reflectivity of 92-98% depending on the wavelength of the light. Granted, aluminum foil isn't the same as pure aluminum, and isn't optimized for reflectivity, but still, according to its thermodynamic properties, there is NO difference between the way aluminum and mylar reflect light. The only difference seems to be that mylar is much easier to work with, which admittedly, is a major advantage.

So here's my question: is there a reason you guys say not to use foil, or are you just repeating what others have said?

Since I have no thermodynamics textbook, I kinda have to accept this on faith, but independend google searches confirm this, unless you inclulde canabis growing communities.

Aluminium foil - Wikipedia
Aluminium - Attributes and Properties of Aluminium Foil

For this reason I feel no need to adapt this post, and would like to use it as opening question.

At the bottom of page one, a user replies:

clovisman

I am a pro-commercial photographer and teach advanced lighting classes at 2 universities- here is a photographers opinion based upon 25years of bouncing light- mylar and foil definetly create hot spots with reflected light- if you use foil first wad it up and spread back out- the wrinkles will bounce the light back in all directions- i have found that nothing beats a satin white surface - there is a much more even distributation of the light rays bouncing off this surface where mylar acts as a lens and will focus light rays if the surface is not completely smooth which is near impossible to do-the room I use to start my plants is white

And this kinda ends the discussion I'd say, from page 2:

khronik

Originally Posted by BeforeYourTime View Post
Holland Hydroponics - Reflective Material

Foil may reflect more heat but mylar wins hands down on light reflectivity.

Originally Posted by elstonite View Post
foil causes hotspots and aint recommended for growing cannabis

Here's the thing: every source I can find that claims aluminum foil is less than 50% reflectivity is inevitably linked to the cannabis-growing community. This leads me to believe there is a pot-growing book out there with misinformation in it about aluminum foil.

Apparently, there is a group out there called the "European Aluminum Foil Association" that knows everything there is to know about aluminum foil. Must be a boring group of folks, but they do know foil! Anyway, here is what they say:

"[Aluminum foil] reflects approximately 98% of radiant heat and light. There is no difference between the reflectivity of a bright and a matte foil surface."

source: alufoil - European Aluminium Foil Association

Yes, I have a lot of free time at work. I told my boss yesterday that I don't have much to do and that he should find me more work but he hasn't yet.

Given this, what remains of the statement that mylar is better, and why are most reflectors made of aluminium, and not some sort of mylar application, if mylar is truly better for the job ? (keeping in mind that the reflective agent in mylar is, aluminium)

Am I missing a bigger picture, where mylar has other properties that make it better over-all ?

 

[PlanetJ]

Re: Foil VS Mylar .. truth or accepted on faith ?

Edited first post with a few extra links and rephrased the question. Thanks in advance for any insights into this.

 

[theengineer]

Re: Foil VS Mylar .. truth or accepted on faith ?

I use foil in my veg area, I just run a toy tank/tractor over it a few times so it's got a mottled finish, and no smooth bits.

I've never bought into the mylar v foil stuff, for many of the reasons you highlight above

 

[PlanetJ]

Re: Foil VS Mylar .. truth or accepted on faith ?

I use foil in my veg area, I just run a toy tank/tractor over it a few times so it's got a mottled finish, and no smooth bits.

I'm using hardboard for walls .. it has a smooth and a somewhat rough area .. I plan on using a doughroller to imprint the pattern of the rough area into the foil, and hope it will diffuse enough to prevent issues with heat.

I've never bought into the mylar v foil stuff, for many of the reasons you highlight above

It either misses a key element that makes it aha! .. or it's just not true I guess

 

[JJ Bones]

Re: Foil VS Mylar .. truth or accepted on faith ?

Foil definitely creates hot spots and does not reflect evenly.

I would say mylar isn't in the A/C reflectors due to how hot it gets in there, they use the other form of aluminum because it can sustain that heat.

 

[PlanetJ]

Re: Foil VS Mylar .. truth or accepted on faith ?

Foil definitely creates hot spots and does not reflect evenly.

Mylar does too, according to the second quote in my opening post ?

I would say mylar isn't in the A/C reflectors due to how hot it gets in there, they use the other form of aluminum because it can sustain that heat.

What other form ?

 

[JJ Bones]

Re: Foil VS Mylar .. truth or accepted on faith ?

I haven't experienced hot spots with mylar before.

I apologize I read somewhere on here someone mention aluminum however I realize I was mistaken.

Here is some great mylar info: What Reflective Materials Can I Use For My Grow Room?

 

[theengineer]

Re: Foil VS Mylar .. truth or accepted on faith ?

to create a hot spot, the aluminium would need to focus the light from the lamp; how does it do this with a mottled surface?

 

[JJ Bones]

Re: Foil VS Mylar .. truth or accepted on faith ?

If using aluminum foil it's best to use the dull side because it diffuses light better. The shiny side is what creates the hot spots

 

[PlanetJ]

Re: Foil VS Mylar .. truth or accepted on faith ?

If using aluminum foil it's best to use the dull side because it diffuses light better. The shiny side is what creates the hot spots

"[Aluminum foil] reflects approximately 98% of radiant heat and light. There is no difference between the reflectivity of a bright and a matte foil surface."

source: alufoil - European Aluminium Foil Association

"While many believe that the different properties keep heat out when wrapped with the shiny finish facing out, and keep heat in with the shiny finish facing inwards, the actual difference is imperceptible without instrumentation.[9] The reflectivity of bright aluminium foil is 88% while dull embossed foil is about 80%.[6]"

source: Wikipedia


I do not want to be stubborn, but the facts seem to contradict this 'common knowledge'.

 

[CO Finest]

The one thing I can throw in there is aluminum foil will retain way more heat. Test your self if you don't believe

 

[Carcass]

Seems to me that retaining some heat on the walls might be preferable to reflecting it back to the leaves of the plant.....(which may be what CO Finest is saying) but to me "shiny is shiny",and I'm a noob,so I'm probably talking through my a$$....

 

[JJ Bones]

No worries PlanetJ, I completely understand what you're saying! Not stubborn you just want the truth and I respect that. I'm always after it myself, so I never claim to always be correct and I'm open to learn

From my experience, the aluminum foil wasn't a great option. I would get hot spots and parts of the leaves were doing funky things as if my light was too close even when it was far away.

What is the source that Wikipedia is citing in your post there? Just curious so I can explore further.

I'm also going to ask some industry folks about this and I'll report back what I find.

 

[PlanetJ]

What is the source that Wikipedia is citing in your post there? Just curious so I can explore further.

Hanlon, J. (1992). 1st ed. Handbook of Package Engineering, Lancaster, Pennsylvaia, and Technomic Publishing: ISBN 0-87762-924-2. Chapter 3 Films and Foils.

 

[theengineer]

reflecting heatspots isn't the preserve of aluminium, and if you mottle the surface of the foil it cannot reflect a specific point, therefore, no heatspot

 

[JJ Bones]

The other thing with foil is, it's kind of a pain to setup especially compared to panda paper. Panda is so cheap, $13 for 10' x 15' or less some places. Stronger, bigger sheets, won't rip easy etc

 

[PlanetJ]

The other thing with foil is, it's kind of a pain to setup especially compared to panda paper. Panda is so cheap, $13 for 10' x 15' or less some places. Stronger, bigger sheets, won't rip easy etc

I'll readily admit that alufoil is not all that easy to work with, but it's not the inferior, almost plant damaging option it is made out to be if you ask me.. I have no heatspots that I can find and my girls seem happy. I did my whole box for $2 on foil and $7 on alu-tape used in floor isolation.

I cant find panda film over here .. they sell black/white film over here .. which is probably the same, but more expensive then what you name there. I wanted this first-grow experience to cost next to nothing and be expendable. The parts that I did not cut back on, are the parts that can be used in a new project, but even there they are the bare minimum for reasonable accuracy and performance .. nothing to write home about. So to invest in a good reflective film, while foil is just as good if I take the time to do it right, would be lazy more then anything

In a serious grow environment, alufoil has no real place .. as it is fragile, and if you upschale from the box I have (61x61x122 cm), it get's expensive fast due to the amount of tape needed to secure the foil, altho maybe your regular wallpaper glue would work. But I'd hate to have to wallpaper with alufoil.

In an I-want-to-get-some-experience high-DIY environment, I'd say it's perfect.

 

[greenergrass]

well i would prefer Mylar over foil because foil will just cripple up and tear mylar is probably more light tight too,

also white reflects more spectrum's of light than either so i would just go with white paint