Reflective Surface (Mylar, Panda Film)
Wall coverings used in indoor grow rooms to bounce stray light back onto the canopy and improve lighting efficiency.
Reflective wall coverings are useful but oversold. A smooth, matte white surface like panda film or flat white paint recovers most of the light a mirror-like Mylar wall would, without the hotspots that can scorch leaves or create uneven canopy light. Diamond-pattern Mylar and 'mirror-finish' claims are largely marketing. The bigger wins in a grow tent come from correct light placement, canopy training, and not having gaps — not from chasing a few extra percentage points of wall reflectance.
Definition
A reflective surface in cannabis cultivation is any wall, ceiling, or floor covering used to bounce photons that miss the canopy back toward the plants. The two most common products are Mylar — a metallized biaxially-oriented polyethylene terephthalate (BoPET) film [1] — and panda film, a coextruded polyethylene sheet that is white on one side and black on the other. Flat white paint is a third widely used option.
What it does
Reflective walls increase the fraction of emitted light that reaches leaves rather than being absorbed by dark surroundings. Horticultural extension guides consistently recommend matte white or reflective films for enclosed grow spaces to improve light-use efficiency and reduce edge-of-canopy shading [2][3]. Strong evidence
Reported reflectance figures (typical, not marketing max):
- Flat white paint: ~85% [3]
- Panda film (white side out): ~85–90% [3]
- Smooth aluminized Mylar: ~90–95% [2]
- Foylon (reinforced Mylar): ~90–95%
Diffuse (matte) surfaces spread reflected light more evenly across the canopy, while specular (mirror-like) surfaces reflect at sharper angles and can create hotspots. Weak / limited
What it doesn't do
Reflective film does not add light to a room — it only recovers light that would otherwise be lost. It cannot compensate for an underpowered fixture or poor light placement. Wrinkled or crumpled Mylar loses much of its theoretical advantage because the folds scatter light in random directions and can focus beams into small hot spots that scorch nearby leaves. Anecdote
Claims that specific patterns ("diamond," "orange peel") boost yield over plain matte white are marketing folklore; there is no published cannabis-specific evidence supporting a yield difference between these finishes. No data
Practical notes
- Install film taut and smooth. Wrinkles matter more than the exact product.
- Panda film is cheap, waterproof, easy to wipe down, and mold-resistant on the black side facing the wall.
- Mylar tears easily and degrades with heat near HID fixtures; keep it away from hot bulbs.
- Flat white latex paint is a legitimate permanent alternative for dedicated rooms [3].
- Most commercial grow tents are already lined with reflective coated fabric; adding more film inside offers diminishing returns.
Sources
- Reported DuPont Teijin Films. 'Mylar Polyester Film — Product Information.' Technical data sheet.
- Government Currey, C.J. & Lopez, R.G. 'Sole-Source Lighting for Controlled-Environment Agriculture.' Purdue Extension HO-296-W, 2015.
- Government Both, A.J. et al. 'Guidelines for Measuring and Reporting Environmental Parameters for Experiments in Greenhouses.' Cornell Cooperative Extension / Rutgers guidance materials on greenhouse reflectance and lighting.
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