I must lightproof and block sunlight in new bedroom. I can't afford blinds or window coverings. I don't use garbage bags, because a plastic bag baking in the sun may emit harmful chemicals (see Home Improvement Stack Exchange).

What happens if sunlight hits and heats up aluminium foil (as suggested on Lifehacks Stack Exchange)? Is aluminium foil safer? Does aluminium foil emit any harms?

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    $\begingroup$ Paste the plastic bag outside the window as mentioned in the linked diy.se thread. $\endgroup$ – Aniruddha Deb Nov 8 '20 at 7:07
  • $\begingroup$ Related: Are modern newspaper inks a health risk? $\endgroup$ – Nilay Ghosh Nov 8 '20 at 9:44
  • $\begingroup$ I think is amongst the best choice. Almost everything can diffuse chemicals. Normally these kind of concerns are for a targeted audience. $\endgroup$ – Alchimista Nov 8 '20 at 12:27

My advice for durability and collecting heat for warming of your dwelling, I would recommend employing the Aluminum foil as a sunblock to the interior of your dwelling.

With respect to safety, Al foil is either rolled annealed 100% Al metal or a high content Aluminum alloy. Further, it may possess a protective clear acrylic sealant, here's a reference, to a now unavailable 2013 article in Material World, quote:

When unsure of whether certain wrappers and packaging are in fact aluminium foil, perform the scrunch test – if the material springs back when scrunched, then it cannot be recycled. Most crisp packets spring back because they are made from plastic film coated in a very thin layer of metal.

Generally speaking, the latter coating is to augment the inertness of the Al foil especially to food acid compositions containing, for example, a mixture of vinegar (Acetic acid) and common salt (Sodium chloride). One can also test for the sealant chemically (by applying vinegar, salt, and gentle warming to a vessel constructed from the Al foil of interest, and observing chemical inertness) or, a bit more subjective, a flame test (where a small sheet of the foil appears to flame-up more than other similar thickness samples).

Now, if an acrylic coating is present, try another heavier brand of foil, as, I do agree it may otherwise be subject to deterioration by UV light exposure releasing problematic breakdown products.

Obviously, using Aluminum foil may present some interior design issues, so here is a source, to quote a historical reference:

The practice of interior design harkens back to the Ancient Egyptians, who decorated their naive mud homes with basic furnishings enhanced by animal skins, simple textiles, graphic biographical and spiritual murals, sculptures, and painted urns.

where, at some point, curtains of varying compositions (including, in the last 50 years, highly reflective) were also marketed.


Aluminium foil does not cause harm, but putting plastics on outer windows side is an option too.

Plastics has disadvantage it deteriorates by UV.

Both becomes weathered during time, so may need replacement for visual reasons.


Living in a room where some dubious compound are present does not mean that it is dangerous. It is a question of dose. Arsenic and lead are lethal poisons. But every human being contains $2.5$ mg arsenic and $3.5$ mg lead. We are used to it.


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