dose the mylar need to be compleatly flat?

jordisgarden

Well-Known Member
it doesnt need to be flat. it just needs to not be bouncing the light away from your plants. my fan moves around my mylar a lot and it is actually making light get all over the room. the light looks like when light bounces off a swimming pool...
in my humble opinion it does not need to be flat, just reflecting towards the plants. when my fan blows and moves the mylar all it does is bounce it all over the place which is a good thing. kinda like a light mover
 

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DownOnWax

Well-Known Member
I know A LOT of people swear by Mylar but I HATE IT!

I painted my walls White and never looked back.
 

TeaTreeOil

Well-Known Member
mirrors are not that reflective they are less reflective than white paint. mirrors refect 80% of the light back at the plants flat white paint reflects 90%. why dont you use white pant?
I've never found one reputable source that claims flat white paint is 90% reflective in the visible spectrum.

Not even close! There's specialty white paint that does. But it's glossy/reflective and not matte house paint.
 

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rotcodnatas

Active Member
OK lets clear this up. Go grab a handheld mirror, now look at an unshaded bulb in the mirror for a few seconds. It messes up your vision right, almost as though you were looking at the bulb directly but not as intense. Now try that with a piece of drywall or plywood painted with flat white, its not the same of course. The problem with mirrors is the angle at which they reflect light but flat white paint is in no way more reflective than a mirror, if it was then why would we have mirrors.
 

jordisgarden

Well-Known Member
just put some damd glossy paint or mylar in there. it doesnt have to be perfect. people get away using nothing. and you have mylar right? so your already ahead of the game...
 

HoldemHigh83

Active Member
what about mylar safety blankets? I've seen these used in the past but most if not all have patterns/stitching. will this lessen the effectiveness of the mylar as a reflector?
 

Mcgician

Well-Known Member
I think mylar is a complete waste of money. Flat white walls are every bit as good in my experience and have none of the headaches of mylar. Spraying, hanging it, buying it, etc. My opinion is, if you need the miniscule difference (under perfect conditions) in reflectivity mylar offers over flat white walls in the first place, you don't have enough light to begin with.
 

rotcodnatas

Active Member
I understand where your comin from Mcgician and to each their own, but i think alot of us here want to get the very most of watever amount of lighting we're using, seeing as it can be one of the more expensive components of everyones favorite hobby/love affair. But at the end of the day a can of paint is much easier for many, not to mention cheaper for the fiscally challenge, especially in these turbulent times. In the end your choice of reflective material is all a matter of personal preference, convenience, or cost; O and I can't forget opinionated arrogance.:wink:
 

TeaTreeOil

Well-Known Member
Yea, like the "don't use foil it causes hot spots!" crazies. "Use mylar!" they endlessly drone. When both are aluminum surfaces and have nearly identical capacity for 'creating' hot spots.

WTF!
 

MAKAVE71

Active Member
i was thinkin it would cause problems that why i asked and i was thinkin about useing mirrors because i have alot in my basement but thanks for answering now i know
 

9inch bigbud

Well-Known Member
Yea, like the "don't use foil it causes hot spots!" crazies. "Use mylar!" they endlessly drone. When both are aluminum surfaces and have nearly identical capacity for 'creating' hot spots.

WTF!
mylar is more reflective out of the 2, its available in wider sizes 1.4m x 100m rolls does not make a loud tin shaking sound when a fan blows across it (stealth) and it must be good for somthing that tin foil is not good for? you dont see NASA lining their space shuttles with tin foil that you buy down the local shop.? is it because its lightweight and better at refecting 97% of the sun's IR heat from cooking the space crew.

it also acts as a better vapor barrier because its plastic and is not as cold as foil so there is less chance of condensation building up on the cold side of your reflective sheating = making your walls grow black mold.
 

TeaTreeOil

Well-Known Member
Mylar is only 90% reflective(avg) over 300-700 nm wavelengths.

As I recall NASA uses carbon composites for heat shields. Reflective Mylar is polyester and aluminum.
 

9inch bigbud

Well-Known Member
Mylar is only 90% reflective(avg) over 300-700 nm wavelengths.

As I recall NASA uses carbon composites for heat shields. Reflective Mylar is polyester and aluminum.

A simple NASA technology that protected Apollo and Skylab is still coming to the rescue in space and on Earth.

NASA has used the same thin, shining insulation material on virtually all manned and unmanned missions. A memorable moment in the insulation's history was seeing its shiny swath around the base of the Apollo lunar landing vehicles.

In 1973 a parasol-type sunshield made of the material helped to save Skylab after the spacecraft lost a heat shield during launch and began to overheat. This dramatic rescue also provided the first possibility of a habitat for astronauts to live and work in space.

Image at right: Teams at NASA's at Marshall Space Flight Center and elsewhere constructed a reflective, parasol-like sunshield to protect Skylab. A second sunshield (pictured here) was installed during the Skylab-3 mission. (Image credit: NASA)

Today, the Hubble Space Telescope and Mars rovers can thank the shiny material for protecting them as they go about business in space.

The silvery insulation is a heavyweight on benefits and a flyweight on mass in order not to weigh down spacecrafts while protecting them. The material is made of a strong, plastic, vacuum-metallized film with an efficient, infrared-reflective coating of aluminum applied as a vapor.

The same properties that are critical in space have proved to be life-saving on Earth. NASA's insulation technology has been widely used to create slim thermal blankets. Perhaps no one can appreciate these benefits more than victims of the earthquake that razed Pakistan, Afghanistan and India in October 2005.


When relief poured into the region, aid included supplies of silver thermal blankets that doubled as ground covers during the day and blankets at night. Two people could also wrap up in the large blankets and share body heat as well as the warmth of the blanket itself.

Image at right: Reflective emergency blankets were used in Pakistan in 2005 after earthquakes devastated the region. (Image credit: Mercy Corps)

Marathon runners can also thank the NASA insulation for making their lives more comfortable. After running long distances in chill temperatures, runners may shiver from more than joy once they cross the finish line and begin a rapid cool-down. As hordes cross the finish line, it may take runners more than 20 minutes to climb into warmer clothes, opening the door to hypothermia. Today many marathons use "space blankets" to ward off the post-race chill. The silver-backed crowds of runners have become a well-known symbol of having finished a race.

Image at right: Marathon runners use reflective blankets to help stabilize body temperatures after a race. (Image credit: AFM, Inc.)

Operating rooms have also used space technology to improve conditions for patients and staff. Insulated bed sheets are used to warm pre- and post-operational patients; for hospital staff members working in chilled environments; and as surgical drapes that give surgeons access to specific areas of the body while keeping the patient warm.

Those who enjoy the outdoors will be glad to know that NASA's insulation technology is an integral part of life-saving gear such as emergency bivvies and rescue blankets. It also provides the simpler comfort of insulated gloves and vests that are supple and flexible, even in extreme cold.

And for those who prefer not to answer the call of the wild, there are still benefits to be found in the space program's legacy. Insulated vests are handy for running in the Iditarod, but also for sedentary hobbies that allow the body to lose heat -- like sewing.

http://www.nasa.gov/vision/earth/technologies/silver_insulation.html
 

relativeood

Well-Known Member
mylar is more reflective out of the 2, its available in wider sizes 1.4m x 100m rolls does not make a loud tin shaking sound when a fan blows across it (stealth) and it must be good for somthing that tin foil is not good for? you dont see NASA lining their space shuttles with tin foil that you buy down the local shop.? is it because its lightweight and better at refecting 97% of the sun's IR heat from cooking the space crew.

it also acts as a better vapor barrier because its plastic and is not as cold as foil so there is less chance of condensation building up on the cold side of your reflective sheating = making your walls grow black mold.


Now THAT is practical! Some good, useful, information about using aluminum foil.

Pretty much anything else said on the subject of aluminum foil is masturbation.
 

highpsi

Well-Known Member
I've been using mylar with a 600w HPS for years and never had a problem with hot spots. If you take your time and apply it correctly then you shouldn't have any problems.
 

TeaTreeOil

Well-Known Member
Congratulations, 9"bigbud, that link doesn't mention mylar anywhere, and instead mentions silver(Ag) insulation. Which is superior to aluminum when reflecting IR.

...the New York City Marathon,
could transform the expense of the silver blankets into
racing revenue through branding....
A&P uses triaxial carbon braid as an alternative to
aluminum or other solid metal in the manufacture of
braided fan containment cases for jet engines.
Hey look, carbon!

...since aluminum is used to build the space shuttle, its
external tank, parts of the reusable solid rocket motor, and
many other shuttle-related components.
Hey look, aluminum!

The insulating material, a strong, plastic, vacuum-
metallized film with a highly-efficient, infrared-reflective,
vapor-deposited coating of aluminum, was created to be
very lightweight in order to minimize weight impact on
vehicle payload while also protecting spacecraft, equip-
ment, and personnel from the extreme temperature
fluctuations of space.
They finally mention Mylar! :-P But to keep it safe from IR and cold! :lol:

The highly pure aluminum coatings are care-
fully matched to their substrates to efficiently redirect
infrared energy—infrared waves being the chief compo-
nent of thermal energy in the near-vacuum conditions
of outer space—to create either first- or second-surface
reflecting. In some instances, the material is intended to
deflect the infrared rays, and in other cases, it is meant to
conserve them as a passive warming system.
And that's how the cookie crumbles.
 

9inch bigbud

Well-Known Member
I've never found one reputable source that claims flat white paint is 90% reflective in the visible spectrum.

Not even close! There's specialty white paint that does. But it's glossy/reflective and not matte house paint.
Diagram of diffuse reflection


Diffuse reflection is the reflection of light from an uneven or granular surface such that an incident ray is seemingly reflected at a number of angles. It is the complement to specular reflection. If a surface is completely nonspecular, the reflected light will be evenly spread over the hemisphere surrounding the surface (2π steradians).
The most familiar example of the distinction between specular and diffuse reflection would be matte and glossy paints as used in home painting. Matte paints have a higher proportion of diffuse reflection, while gloss paints have a greater part of specular reflection.
Diffuse interreflection is a process whereby light reflected from an object strikes other objects in the surrounding area, illuminating them. Diffuse interreflection specifically describes light reflected from objects which are not shiny or specular. In real life terms what this means is that light is reflected off non-shiny surfaces such as the ground, walls, or fabric, to reach areas not directly in view of a light source. If the diffuse surface is colored, the reflected light is also colored, resulting in similar coloration of surrounding objects.

Three bi-directional diffuse reflection (BRDF) models


In 3D computer graphics, diffuse interreflection is an important component of global illumination. There are a number of ways to model diffuse interreflection when rendering a scene. Radiosity and photon mapping are two commonly used methods.
http://en.wikipedia.org/wiki/Diffuse_reflection

agro mylar is 97% reflective the thin stuff is 95%.

the bright side of aluminium foil is 88% while dull is about 80% http://en.wikipedia.org/wiki/Aluminum_foil#cite_note-Hanlon-3

10% is 10% more light it all adds up.
 

TeaTreeOil

Well-Known Member
Yes, I've done the ray tracing. Using radiosity and photon mapping.

Aluminum is twenty-six times as effective in producing lux on an illuminated surface compared to matte white.
 

9inch bigbud

Well-Known Member
Congratulations, 9"bigbud, that link doesn't mention mylar anywhere, and instead mentions silver(Ag) insulation. Which is superior to aluminum when reflecting IR.





Hey look, carbon!



Hey look, aluminum!



They finally mention Mylar! :-P But to keep it safe from IR and cold! :lol:



And that's how the cookie crumbles.
its mylar:sleep:http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940006703_1994006703.pdf

BACKGROUND INFORMATION
Mylar film is transparent, tough, and flexible. The material exhibits properties such as low water
absorption; dimensional stability; resistance to oils, fats, and many chemicals; and has a very low permeability
to gases and odoriferous substances. O and S are two types of Mylar; O is highly transparent;
and S is slightly opaque, has improved slip or handling characteristics, and is available in several widths
and gauges. The material has a variety of applications, with the most prominent being electrical. For
example, the 100-gauge film is suitable for electrical capacitors, electrical motor slot-liners, and for
other insulation applications involving cables, coils, and transformers. The material is free from plasticisers
or other additives; therefore, metallization by the vacuum process is easy. Mylar was also used as
the construction material of the American communications satellite, Echo I of 1960, in the Stratoscope
balloon telescopic system, and the Ranger lunar surface exploration vehicles.1

The chemical name for Mylar is polyethylene terephthalate which is a saturated polyester. The
name, Mylar, is a trade name for the material used by Du Pont, the primary manufacturer of Mylar in the
U.S. Polyethylene terephthaiate film has a high thermal stability. Over the temperature range of-20 to 80°C, thephysicalandmechanicalpropertiesof Mylar showlittle change.Thefilm retainsusefulpropertiesrangingfrom
150to 175°C,andnoembrittlementoccursat temperaturesaslow as-60 °C. The
film remainsflexible attemperaturesaslow as-50 °C3
 

9inch bigbud

Well-Known Member
Yes, I've done the ray tracing. Using radiosity and photon mapping.

Aluminum is twenty-six times as effective in producing lux on an illuminated surface compared to matte white.
have you got a light meter? do you do experiments in the grow room? if you have one?? or just play with your PC all day posting graphes that do not add up? after all its only a simulation it is not real other people go in to the grow room and put things like light meters under lights and take readings from different materials to show what works best " THEY DO IT" you play about on the PC! These people make money from doing these experiments writing books on growing they have seen loads of grow rooms you have seen just 1 and thats under a small CFL light ( even if its that) come on tree who is going to take someone seriously who just posts make believe simulation rendering garbage and calls him self an expert that grow under CFL's?

I play microsoft flight aviation simulator and have been playing it for years and years does that make me an aircraft pilot?
 
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