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Mylar vs flat white paint

stemarmel

New member
Hi friends!!
New grower constructing my grow room and was curious for some input from experienced growers as to their preference between lining the grow room with Mylar as opposed to painting the walls with flat white paint.
Any advice is much appreciated thanks!!!
 

Scrappy-doo

Well-known member
Veteran
Flat white is considered superior because it diffuses light better and reflects more of the full spectrum than Mylar. Orca film is supposed to be the best reflective material available to most of us atm. There's a great comparison video of orca vs Mylar on YouTube. If price is an issue go with flat white.
 

vostok

Active member
Veteran
The only guys who post this are the rich noobs, but thats OK, I go flat white every time ..
although if you are growing in a shoe box even a pc box, mylar could be a cheaper option ..flat white paint is best, and when the room is not in use ...it looks good too?

ps go for a good quality paint with a lot of titanium oxides the stuff that makes it white!
 

Granger2

Active member
Veteran
I've gotten No VOC white white paint from HD and Lowe's. The 1 I got last was called paint & primer. Both took 2 coats, and I used a paint...uh...can't remember what they're called. [too mush juana]. Paint pad, I think, but I like it cuz you can smear it on thick. Get indoor scrubable. The difference of 5% approx amounts to very little difference for the savings. Good luck. -granger
 

EclipseFour20

aka "Doc"
Veteran
I am in the "high gloss" paint camp...as flat paint "absorbs light"---gloss paint "reflects light". Sometimes "stoner logic" is the opposite of what is "correct".

A repost of one of my earlier posts--

Google: "table 2-16 Light Reflection"...and google books should take you to page 217 of "CRC Handbook of Tables for Applied Engineering Science" where Table 2-16. Light Reflection and Transmission is published, (sorry not able to cut & paste...for some reason) so below are few items to compare.

Polished silver, 95% reflectance
White plastic, 78%
White gloss paint, 75%
Aluminum paint, 60%


Now as to paint sheen (flat, satin, semi-gloss, high-gloss)--

Google: "2.5 Reflectance measurements" "color for science"...and google books should take you to page 68--of the book "Color for Science, Art and Technology"...which concluded:

2.5. Reflectance measurements
2,5.1. Specular and diffuse reflectance
If a beam of light shines on a mirror at 45° to its normal, it will be entirely reflected
in the opposite direction at the same angle as shown in fig. 2.20 at (a). This mirror-like
effect is called specular or regular reflection. For all practical purposes, the light does
not enter the material from which the mirror is made but is reflected only by its front
surface.
If a beam of light shines on the flat surface of a compressed pellet of barium sulfate
powder at 45° to its normal, the beam will penetrate the surface and enter into the body of
the pellet. Particles of barium sulfate will scatter, i.e., redirect, the light in many different
directions. After being scattered many times the light will find its way out of the pellet.

picture.php


The light leaving the pellet will exit at many angles from the normal as shown in fig.
2.20 at (b). This is called diffuse reflection.
Light reflected from a highly glossy white paint film will have both a specular and
a diffuse component
as shown in fig. 2.20 at (c). A paint film is made up of pigment
particles held together in a resin binder. Specular reflection occurs at the resin/air interface
and constitutes about 4 percent of the light incident on the film. The remaining light
enters the film, is scattered by the titanium dioxide pigments in the paint and is diffusely
reflected. High gloss materials have very smooth surfaces and the specular component
of the reflection becomes a narrow beam.
As the gloss of a material decreases, its surface becomes rougher. The specular reflection
is a wider beam of less intensity at the specular (mirror) angle as shown in fig. 2.20
at (d). As the gloss decreases further, the specular peak widens until it disappears for a
very matte material. A very matte (flat) white paint will exhibit only diffuse reflectance.



Link to the 511 page book in pdf format (25 meg)...http://dcis.uohyd.ernet.in/~mravi/downloads/CIP/CIP-EBOOKS/color%20science%20for%20technology.pdf

All paint experts share the same opinion, higher the gloss, greater the reflection--lower the gloss, greater the absorption. Some define "absorption" and "reflection" as opposites, such that Reflection Rate = 1 - Absorption Rate (ie, item with 75% Reflection is then limited to maximum of 25% Absorption rate).

My floors, walls and ceilings are painted with high-gloss white--easy to see what's dirty and easy to maintain/repaint.
 

prune

Active member
Veteran
White looks nice, mylar distracts - but if you're relying on reflectivity for contributing to production in any meaningful manner you will be sorely disappointed. Our eyes notice reflected light, chloroplasts don't.
 

Jhhnn

Active member
Veteran
White looks nice, mylar distracts - but if you're relying on reflectivity for contributing to production in any meaningful manner you will be sorely disappointed. Our eyes notice reflected light, chloroplasts don't.

Please. Photons are photons, direct from the source or reflected. It makes no difference. Similarly, gloss, the ability to reflect an image, makes no difference either. Plants don't see images. They absorb photons. A high gloss black surface reflects an image but very little light.

The difference in reflectivity between brilliant flat white paint & films is so low as to be a non-factor in comparison to all the other factors determining yield. Both beat non-reflective surfaces in a grow area.

Flat white latex paint offers certain advantages. It's inexpensive, permanent, easy to apply & washable. It diffuses light as it reflects, thus softening shadows & giving more even light distribution within the grow area. It provides no hidden refuge for pests & disease.

Cheap paint sux. Spend a little more for good stuff, like Benjamin Moore- be happy using it & with the results.
 

EclipseFour20

aka "Doc"
Veteran
Ahhh...but remember there is an equilibrium between "reflection" and "absorption", as the sum of the two will always equal to "1", ie--if a certain paint is 70% reflective, then it is also absorbs 30%.

Another way of thinking about it is, heat and light absorption go hand in hand; hence an object painted black and placed in the sun will be warmer (reflect less light) than the same thing painted white (cooler and reflects more).

But why do some people suggest "flat white" over "high gloss white" for grow rooms? It is because light waves reflect MORE EVENLY on flat/matte surfaces...or specifically the light is more "evenly diffused" with little to zero hot-cold spots. On the other hand, light waves reflected on "high gloss" surface (same color) will always produce a greater amount of lumens, flux, par, etc because of the "hot spots"--or as referred to in the above graphs, "specular reflection". Gloss = more light but less even reflection, flat = less light but more even reflection.

Every chart I've seen comparing certain reflective/absorption qualities of various materials has always concluded that a "high gloss" or "semi gloss" painted surface has superior reflection numbers than "flat paint".

BTW...I agree with Jhhnn, a review of photosynthesis 101 shows plants absorb both direct and reflected light. In fact, the exact amount of "light" which a plant leaf does not "absorb" is actually "reflected". (Sum of the two must always equal "1").
 

Jhhnn

Active member
Veteran
Ahhh...but remember there is an equilibrium between "reflection" and "absorption", as the sum of the two will always equal to "1", ie--if a certain paint is 70% reflective, then it is also absorbs 30%.

Another way of thinking about it is, heat and light absorption go hand in hand; hence an object painted black and placed in the sun will be warmer (reflect less light) than the same thing painted white (cooler and reflects more).

But why do some people suggest "flat white" over "high gloss white" for grow rooms? It is because light waves reflect MORE EVENLY on flat/matte surfaces...or specifically the light is more "evenly diffused" with little to zero hot-cold spots. On the other hand, light waves reflected on "high gloss" surface (same color) will always produce a greater amount of lumens, flux, par, etc because of the "hot spots"--or as referred to in the above graphs, "specular reflection". Gloss = more light but less even refection, flat = less light but more even reflection.

Every chart I've seen comparing certain reflective/absorption qualities of various materials has always concluded that a "high gloss" or "semi gloss" painted surface has superior reflection numbers than "flat paint".

BTW...I agree with Jhhnn, a review of photosynthesis 101 shows plants absorb both direct and reflected light. In fact, the exact amount of "light" which a plant leaf does not "absorb" is actually "reflected". (Sum of the two must always equal "1").

I seriously doubt that there's a gnat's ass worth of difference in reflectivity between gloss & flat white paint of the same brand. The only advantage to flat is that it creates a more even dispersion of light throughout the space, something useful to growers.
 

iTarzan

Well-known member
Veteran
Reflextixs is 94% reflective and easy to handle. Plus it has a much higher insulation factor which helps hide a heat signature. I like flat white paint too though. It is the most economical but you do have to paint which can be a PITA.
 

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