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Reflective Mulch Info: Is Reflective Mulch Effective In Gardens

If you’re tired of the aphids spreading diseases to your crops, maybe you should be using reflective mulch. What is reflective mulch and is it effective? Keep reading to find out how reflective mulch works and other reflective mulch info.

What is Reflective Mulch?

Reflective mulches are reflective material such as aluminum or silver polyethylene mulch that reflects light up onto the leaves of plants. They are great for gardeners growing in partially shady conditions. They also come in colors such as silver, yellow, orange and red that has been reported to be effective for management of certain pests and, thus, possible virus transmission.

How Does Reflective Mulch Work?

As mentioned, reflective mulch increases the amount of light available to plants but it also increases air temperature, and photosynthesis, which means better growth.

Reflective mulches utilize the entire light spectrum, thereby boosting the available amount of light and heat to plants resulting in higher yields and bigger fruit and vegetables. It

also helps retard weeds and conserve moisture just as other forms of mulch in gardens.

Additional Reflective Mulch Info

Reflective mulch not only increases temperatures and the amount of available light to plants, but it has been shown to reduce damage caused by certain insect pests such as aphids that transmit disease. It may also deter bird pests.

Is reflective mulch effective against pests? While some of the colored reflective films have been reported as more effective than white or black plastic mulches for management of pests, they are not effective on a wide array of pests. Each color of mulch seems to do a better job of repelling a certain pest while others have even increased pest levels.

Also, the effectiveness of reflective mulches seems to decline through the season as more of the visible surface is covered by the growing plant or as colors fade in the sun.

For the most part, however, reflective mulch benefits outweigh the potential detriments. Even cost doesn’t have to be a factor since you can make them cheaply out of aluminum foil and cardboard that has been painted white.

Using Reflective Mulch

To use reflective mulch, first remove any weeds from the bed. Then cover the bed with silver polyethylene mulch, which is available in rolls. Bury the edges with soil or hold them down with stakes, rocks, etc. Once the mulch is in place, cut 3- to 4-inch (8-10 cm.) diameter holes and plant a few seeds or a single transplant within the hole.

Or, if your budget is limited, cover cardboard with aluminum foil. Likewise, if you already have it, spray clear plastic mulch or landscape fabric with reflective silver paint.

When temperatures peak, be sure to remove the mulch to avoid overheating and burning the plants.

Growing marijuana has changed over the years with more people doing it today than they did a couple of years back. One of the main reasons for the growth is because today, there are easier and faster growing methods. Many people are moving away from tradition and embracing grow room, grow tent, hydroponics, and led grow lights marijuana growing among others. This kind of farming is both discreet and it means you no longer have to buy marijuana from anyone again because you can finally have your own right at your doorstep. Besides being discreet, the method is also easy, the crop grows fast and you do not need excellent weather and temperature conditions to grow your cannabis. The harvest turnaround time is anything between 4 to 5 months.

Besides nutrients and water, MARIJUANA also needs enough light to help with photosynthesis which many grow rooms unfortunately cannot tap too well. However with the help of reflective materials, grow rooms are able to use light for the proper growth of cannabis. A reflective light increases the intensity of the light in a grow room spreading it evenly across the room. You do not even need more than one light in a grow room if you have reflective material. Using a reflective material increases the light by over 30%. Reflective materials therefore help in cutting down energy costs. It is also good to note that reflective materials come in different types. Before we look at the different types of reflective materials, below is a look at our pick of the best reflective material for grow rooms

Our Top Picks of The Best Reflective Material

Apollo Horticulture 2 Mil Reflective Mylar Sheet Roll

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(Last update on 2019-04-25 at 08:24 ,UTC)

When you start using Apollo Horticulture Reflective Material for your grow room, trust that you can produce more from your plants. Even though the product is one of the lowest priced in the market, the reflective material gets the best out of grow lights to give your marijuana plants quality growth. Known for its consistency and unmatched quality, Apollo Horticulture, gets better with every product. You will believe this once you start using any of their products and especially the Apollo Reflective Material.

The 2-mil reflective material roll measures 4’x100’ with widths of 48”, length of 50” per roll and a diameter of 2.25”. The highly reflective polyester material reflects anything between 92% and 98% of light. The material has the ability to increase light intensity without changing the amount of electricity used in the grow room. Grow room heat stays at the right temperature during the whole growth period, which helps the crops to thrive and yield more.

The material does not bleed with water and the best part is that you can see through it. This means that you can monitor your crops without necessarily going into the grow room unless it is necessary to do so. With this material, your marijuana is also safe from chemicals in the air because Apollo horticulture reflective martial protects them. You will definitely not go wrong with this product.

Earth Start Mylar Reflective Material

-$21.64 OFFBuy on Amazon

(Last update on 2019-05-30 at 04:55 ,UTC)

Mylar is one of the most inexpensive ways to reflect the light in your grow room to concentrate on the growing space. The new and improved design REFLECTIVE MYLAR MATERIAL from Earth Start is a durable 2-mil grade that also comes with a poly backing that acts as a vapor barrier. Mylar material is easy to fix and even people growing crops and using the reflective material or the first time can do it. All you need for fixing the material in place are staples or thumbtacks and very little strength. Both sides of the material are metalized and the material does not tear or bleed water. The material does not give the same reflection a mirror would but you can see your reflection on the reflective Mylar material.

NAVADEAL Silver Reflective Mylar Film

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(Last update on 2019-05-30 at 04:04 ,UTC)

Do not let your crops stall or the beautiful green foliage of your marijuana plants look dull when you have an effective Mylar reflective to help you out of the predicament. The NAVADEAL Silver Reflective Mylar Film is another inexpensive way to make sure that your crops get the best out of the grow lights. The material is environmental friendly and made with very high quality VMPET with both sides metalized and pet coated to resist wear, tear and corrosion. Used in indoor gardening, the Mylar reflective film reflects light from the grow lights back to the crops in order to increase their growth by giving optimum reflectivity.

The film reduces all the red spots in the grow room and spreads light evenly to cover all the crops. This is important especially for the crops that are not directly under a single grow light that cannot spread light to a larger area. The film reflects 95% of the light particles, which is efficient for excellent growth. The material is tear proof, puncture proof, made in the USA, eco-friendly, durable and easy to tack or tape into a flat surface or the wall. It comes with 100% satisfaction guarantee. To fix the Mylar film, use an adhesive spray or tape. The Mylar film package includes two sheets of the film with each sheet measuring 82”x47”.

VIVOSUN Horticulture Highly Reflective Material

-$8.96 OFFBuy on Amazon

(Last update on 2019-05-30 at 04:04 ,UTC)

VIVOSUN horticulture is not new to anyone doing indoor farming. It is a name synonymous with hydroponics and other farming methods. VIVOSUN also has some of the most quality Hydroponics Equipment in the market. VIVOSUN, which highly believes in manufacturing eco-friendly products, brings you this quality highly reflective material for the growth of your marijuana crops. The material, made from high quality heat resistant and tear free material, increases the growth pace and volume from additional light.

The material is durable and ideal for hydroponic grow room gardening and other indoor door gardening is water proof, corrosion resistance, age resistance, puncture resistant and very easy to mount. The 2-mil 48” material is 100 ft. and reflects 92% to 97% of the light from the bulb. For safe storage, the material comes with a sealing cover at the bottom.

PMU – Hydroponics Mylar Standard 2 Mil Reflective Material

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(Last update on 2019-04-25 at 08:25 ,UTC)

Mylar is the most popular and best reflective material to use on your indoor crops. Besides being very affordable, it is also very efficient and allows even distribution of light in your grow room. The above 2-mil standard hydroponics Mylar film reflects around 98% light to the crops. The double metalized film measures 48” wide and 100‘ long. The material also helps to reflect light from outside the grow room into the crops allowing all the plants to benefit from the light distribution. The metallic film is easy to set up and easy to maintain. Every package comes with one roll.

Best Paint for Reflecting Light

Rust-Oleum Ultra Matte Chalked Paint

-$1.01 OFFBuy on Amazon

(Last update on 2019-04-25 at 08:25 ,UTC)

As much as reflective materials are the most common light reflectors in grow rooms, there are other alternatives too. One of the most common alternatives is reflecting light. If the walls of a grow room are too dark, then a reflective coat of paint would instantly change then to be more accommodating for proper plant growth. One of the most quality light reelecting paints is Ultra-Matte Chalked Paint by Rust-Oleum and it makes the perfect alternative for a reflective material. The paint is versatile and you can use on different materials such as wood, metal and ceramic.

The paint texture is latex and it emits a minimal smell unlike many other paint brands. Latex material is also easy to clean. One other reason why the paint is very popular is its ease of application. It glides through the surface effortlessly and dries up in just 30 minutes after application. The paint comes in a 30-ounce container. This roughly translates to slightly over 800 ml, which is enough to cover an area of 150 square feet. The other advantage is that unlike many other paints where you need to paint several coats to get the final effect, with Rust-Oleum, you only need one coat and you are good to go.

The only time you might need another coat is if your grow room walls are wood. In this case, you will need a primer to accompany the paint. In spite of its effectiveness, the paint is also affordable and it allows your plants to grow with enough light this increasing their strength and yield.

Best Grow Light Reflector Tent

iPower 95”x48”x78” Hydroponic Water Resistant Grow Tent

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(Last update on 2019-05-16 at 04:25 ,UTC)

If you want to get the best out of your marijuana crop, invest in a good grow tent that comes with a reflective FOYLON material already fitted. This will save you the need to go purchase a reflective material and start the process of fixing it all together. iPower saves you so much trouble by introducing one of the best hydroponic tents in the market. The grow tent comes with a water resistant MYLAR REFLECTIVE SHEETING on both sides. The water resistant reflective sheeting is 99% light proof and measures about five by five feet.

Being light proof means that the sheet has complete protection from what is in the environment, making it ideal for cannabis growth. The sheet is easy to use as it comes with premium zippers that you can open and close easily. To make the material even more efficient and last longer, it has double stitching all around. This helps to prevent any outside light from penetrating into the grow tent. The tent is also sturdy as it comes with metal poles that stand upright and able to withstand pressure.

A removable water resistant cover and a convenience organisation bag are other items that come with the grow tent. To make your growing been more fulfilling, the tent comes with one-year manufacturer’s warranty, which means that you can take it back for a full refund if it does not perform. The tent has ventilation holes for air circulation, which is another important aspect for the proper growth of your weed.

What to consider when buying the best reflective material for grow room

We have highlighted some of the best reflective materials in the market today but there are hundreds of other options in the market. Before you go looking for the best reflective material to use in your grow room, you need to know exactly what you are looking for. Below are some of the most important things to consider.

Reflective material options

Choosing the right material may seem overwhelming especially if you do not know which reflective material is better than the other and which one suits your grow room best. Below are the most popular reflective material options in the market to make it easier to understand what you are looking for in a reflective material.

Mylar reflective material

This is by far the most popular reflective material used in indoor farming. One of the reasons for its popularity is the ability to reflect more than 95% of light. Sometimes the reflection is close to 100%. Mylar is made of a polyesters film that measures anything from one millimetre to two millimetres. Besides being, the most popular and most affordable, Mylar material has some setbacks.

For starters when you have Mylar reflective material in the grow room, you need to have ventilation too because the material produces radiant heat. Too much of this heat may be damaging to the weed and you therefore need to let in some cool air to neutralise the heat.

Another disadvantage is some of the Mylar materials may be prone to tear and puncture so there will be need for frequent replacements. These however are minimal problems compared to the benefits.

Paint reflective material

Paint is readily available and the other best alternative to polyester reflective materials. Some people use cabinets as their grow rooms while others wooden cubicles. These setups do not get enough light into the crops and in order to capture light, you can use flat white paint to reflect light back to the crops the budget friendly alternative can reflect anything between 85% and 95% of light.

One of the major benefits of using paint over other options is that it is easier to clean and maintain. The latex material that makes the paint is smooth and easily dusts off after just a wipe. Paint unlike Mylar reflective material does not produce too much heat which makes the interior of the grow room remain cool at all times. If you apply the paint correctly, you will have even distribution of light without any air pockets or hotspots and red spots.

Foylon reflective material

Not many people can tell the difference between the Foylon reflective material and the Mylar reflective material. The two look similar and come with many other similarities besides the look. However, there is one distinctive feature that sets the two apart. Foylon is a more expensive reflective material and the reason is that it is much more durable than Mylar. Foylon is not made from just polyester but from spun polyester. A foil laminator is used as reinforcement on the material to make it stronger. The reinforcements also ensure that the reflective material does not fade and it allows over 95% percent of light to bounce back to the grow room.

Grow tent reflector material

This is also another very popular alternative with many marijuana growers. The option of a grow tent that comes with its own fitted reflective material is a stress free option too. The material on the grow tent can be anything from Mylar to Foylon. The built in materials do not require any fixing or stapling.

Plastic reflective material

Though not as popular as the above-mentioned options, plastic, also referred to as black or white polymer is another option that grow room farmers use as reflective materials. The plastic, which is white on one side and black on the other, has the ability to reflect up to 95% of light back to the crops. The thicker the plastic the more durable it is so if to ever decide to go for this option, do not go for thin sheets of plastic. One of the main disdvantages why this option is not very popular with marijuana growers is that plastic produces too much heat, which can stress the crop. In order to avoid the plastic from getting too hot you have to keep it far from the grow light, which could be difficult in some situations especially in small, grow rooms.


Before you go buying the reflective material for your grow room, you should also take into consideration the temperature of the space. If the room is cold, go with Foylon, or Mylar reflective materials. If the temperatures into room are high, go with the paint reflective option.

Wrapping it up

The success of growing healthy marijuana crops lies on the essentials and detail. Light is one of the most important essentials and therefore you should pay enough attention to the details of the reflective materials you choose. Whatever type of material you choose, the most important fact to take into detail is that whatever you choose increases the intensity of the light in the grow room efficiently. This means that light covers every crop in the room to ensure the environment is suitable for your crops. We hope with the above best reflective material for grow room, you will know what to expect when you need light for your crops.

Top 5 Best Selling Reflective Material On Amazon:

# Preview Product Rating
1 VIVOSUN Horticulture Highly Reflective Mylar Film Roll 4FT x 100FT 2 Mil 232 Reviews on Amazon Buy on Amazon
2 NAVAdeal Silver Reflective Mylar Film- 82 x 47 Inch Set of 2- Garden Greenhouse Covering Foil… 113 Reviews on Amazon Buy on Amazon
3 VIVOSUN 6 Mil Mylar Film Roll 4 FT X 10 FT Diamond Film Foil Roll Highly Reflective Grow Room (10… 89 Reviews on Amazon Buy on Amazon
4 Reflectix BP48010 ubble Pack Insulation, 48 in. x 10 ft. 311 Reviews on Amazon Buy on Amazon
5 6 Yard 2 Inch Width Fabric Reflective Webbing Green for Sew On 8 Reviews on Amazon Buy on Amazon

5 / 5 ( 1 vote )

Every day you operate your indoor cannabis grow room, you’re forking out money on electricity to run your grow lights. Light is, after all, an essential nutrient for your plants. You want every watt of electricity that goes into your grow lights to generate light energy that reaches leaves, so they can engage in life-sustaining photosynthesis to fuel plant growth.

For this reason, reflectivity is a big deal in grow rooms.

Part of the reflectivity game begins with the type of reflector hood you pair with a high-intensity discharge (HID) grow light.

Growers using light-emitting diodes (LED) grow lights don’t have to worry about this, in part because the diodes are encased in a material that functions as a reflector.

The wall reflectivity of your cannabis grow room has a massive impact on how much light reaches your plants’ leaves, and how much light is wasted. Light emanates downward and outward from LED grow lights and HID reflectors. Approximately 20–40 percent of it hits grow-room walls. You want as much of that light as possible to bounce back from the walls and onto your plants.

One way to ensure this is to make sure your grow space adequately fits the number of plants you’re growing. Light intensity drops off with distance, so the further the plants on the outside edge of your garden are from the walls, the less light will reflect onto them.

Make sure that no plants are touching the walls by keeping a gap of 3–4 inches between the walls and the plants to allow for airflow.

Wall Wisdom: How To Make Your Grow Room Reflective

One important choice growers must make is what they put on their walls to positively impact light reflectivity. The main choices are a coat of white paint, or an adhesive sheeted material.

Flat White Paint

Paint can sometimes be the easiest choice from a logistics perspective. Once you’ve painted the grow room, you don’t need to do anything else to the walls, and there should be no need to place additional material on top of the painted surface.

The smartest paint choice is a high reflectivity flat white interior paint that’s designed to repel molds, fungi and mildews, and has little if any off-gassing volatiles in it.

When properly applied, flat white paint reflects 75–85 percent of the light that reaches it. It’s even better if walls and ceilings are flat surfaced, rather than having an orange-peel, textured or bumpy finish. Using flat white paint on a flat wall, you get uniform bounce-back of light — but there can be as much as a 25 percent loss due to the paint’s reflectivity limits.

And white-paint reflectivity ratio isn’t as high as with Mylar or Panda Film.

On the other hand, with paint you don’t have to worry about wrinkling, and there’s nothing to mount to or concerns of the material falling off the wall. Plus, a painted wall is easy to clean.

Mylar Reflective Sheets

This loss of reflectivity is why many growers avoid the paint option in favor of using materials that attach to walls and offer higher reflectivity. Of these, the most reflective is Mylar, a thin, opaque material that looks like a sheet of silver.

Admittedly, it is tricky to attach Mylar to walls, and especially difficult to fix it to ceilings, because it’s a thin material that can easily rip, wrinkle or scratch. Mylar should be applied with the same amount of care as one would apply a window-tinting film on a car. The material must be absolutely flush to the wall, with no bends or wrinkles.

Any wrinkles in any kind of reflective material will create hot spots and dark spots. A hot spot is a concentration of light energy, while a dark spot is a deficit of light energy. When reflective materials are wrinkled, bent, or otherwise not flush to wall surfaces, they don’t reflect light evenly.

Mylar and general reflective sheeting materials must be attached securely so they don’t catch fan air and ripple with air movement. Many growers use Velcro to attach 2 Mil Mylar to walls (always use the thickest Mylar you can find). I use white Gorilla Tape, and as little of it as possible, which works well, unless you have inferior humidity control, which will cause your interior walls to sweat and the tape to loosen.

As with all silver-sheet reflective materials (including Foylon metallic sheeting), Mylar reflects heat radiation, not just light radiation. This isn’t desirable, and it’s one of many reasons why you want aeration fans blowing through your plant canopy whenever grow lights are on, and also a climate control system with enough capacity to remove excess grow-room heat.

Mylar is fragile and difficult to work with. If you foliar spray your plants and drops of water get on your Mylar-covered walls, or if the air in your grow room isn’t well filtered, the surface reflectivity may be dimmed by droplets or dust, and it’s hard to clean without tearing or leaving streaks.

While reflective sheets can prove burdensome to mount flush to walls, they do offer the highest reflectivity of any material, and as an added and unexpected benefit, they give you trippy visuals, much like a carnival trick mirror. (I confess to many evenings seeing cosmic meaning in the patterns of reflections that shimmered in my Mylar as it shifted in the fan breeze — after inhaling a pure sativa, of course.)

Panda Film

The most popular reflectivity material is white poly plastic, popularized under the brand Panda Film. I use the thickest version of this plastic sheeting I can find. It has a highly reflective white coating on one side, and black coating on the other.

Panda Film reflects 75–89 percent of the light that hits it and is much more rugged than even the thickest Mylar. It’s easy to clean and hang, and is cost-effective and versatile in ways many growers don’t yet even know about.

Indeed, I’ve used Panda Film as movable grow-room walls by affixing the sheets to the ceiling as a way of framing my grow space, with lead weights on the bottom to keep the sheets from blowing in the fan wind. The plastic served as my grow-room walls, and I could sculpt its placement to precisely match my plant spacing, so the leaves always got maximum bounce-back of light. It’s like a custom-sizable grow tent without a frame.

Dimpled German Aluminum

We’ve seen grow ops with walls covered in dimpled German aluminum, the same material used in the highest-quality grow-light reflectors. It was an expensive option, but the reflectivity was about 95 percent, and the material was easier to clean and more durable than Panda, Mylar or paint. It used to be that you could buy big plates of dimpled aluminum at a grow shop, but we haven’t been able to find it in recent times.

Clearly, each of these reflectivity options has its own advantages and disadvantages.

Bad Choices For Grow-Room Walls: Mirrors And Aluminum Foil

Growers have been known to use other reflective materials, but none are worth the effort and can be unsafe. Mirrors, for example, are a very bad choice, as they absorb light, and reflectivity can be as low as 50 percent. Also, they break.

Aluminum foil is another bad choice. It offers less than 50 percent reflectivity, has a tendency to wrinkle and bend, is difficult to mount and clean, it can cut you, and worst of all, it conducts electricity.

Some growers use thermal blankets, infrared blockers and similar materials, if those materials have a highly reflective coating on at least one side. Infrared blockers are particularly useful if you suspect police and/or thieves are using infrared detection devices to scan dwellings in your area, looking for the telltale heat signatures of grow lights.

In some prohibitionist states, police routinely fly aerial patrols using manned aircraft or drones that have infrared radar to see thermal data through walls and roofs. Police may use this data to convince a judge to sign a search warrant.

Thieves use thermal detection drones and handheld devices to gather the same kind of data, which they then use to identify grow ops they can later rob.

Infrared blocking material is only useful on ceilings and for external walls to discourage infrared scanning. Otherwise, it’s not an ideal reflective material in an indoor grow room because it traps heat, is expensive, thick, and tough to mount.

So, you now know the good and the bad about cannabis grow-room reflective materials. Mylar and dimpled German aluminum are the top picks, while Panda Film is a close second, followed by flat white paint at a distant third. The bottom line is this: Get as much light onto your indoor marijuana plants as possible, so every penny you pay for grow-light electricity generates the fattest buds possible.

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Since aluminum foil has a shiny side and a dull side, many cooking resources say that when cooking foods wrapped or covered with aluminum foil, the shiny side should be down, facing the food, and the dull side up. This is because the shiny side is more reflective and so will reflect more of the radiant heat than the duller side.

Is this true?

Although most resources still say it is true, the shiny side should be down, some newer sources say that it makes no difference which side of the aluminum foil faces up.

For example, Robert L. Wolke in What Einstein Told His Cook and America’s Test Kitchen say that it makes no difference at all in cooking. You can place either side in either direction whether cooking or freezing food with aluminum foil.

Leifheit 4-in-1 Wall-Mount Paper Towel Holder | Plastic Wrap and Foil Dispenser with Spice Rack

However, their explanations make little sense. They are in effect pseudo-explanations.

Both sources provide the following, similar explanation (paraphrased):

Aluminum foil has a shiny side and a dull side. Many people believe that it matters which side is used up or down. The truth is that it makes no difference at all. The reason the two sides look different is due to the manufacturing process. When the sheets of aluminum are rolled out, the side that comes in contact with the rollers come out shiny..

This explanation does not explain why the shiny side makes no difference. It simply reiterates, with a bit more explanation, that foil does, in fact, have a shiny side and a dull side. Not very informative!

Regardless of why one side of aluminum foil is shiny and one is dull, it stands to reason that the shinier surface will be more reflective than the duller surface. The explanations given seem to indicate that since the shiny and dull sides are simply a by-product of the manufacturing process and are not purposely put there, they make no difference. The explanation does not support the claim. So what’s the truth?

The truth is that the shiny side of aluminum foil is only a little bit shinier than the dull side. While some small amount of additional energy will be reflected by the shiny side, the difference is so small that it will make no practical difference in cooking. To say that there is no effect whatsoever is inaccurate and it probably still is a little more efficient to cook with the dull side out. However, when measured over time in high temperatures, the difference is so slight that there should be little discernable change in cooking times. This may seem like a lot of explanation to come to the same conclusion, but it is not my purpose to give inaccurate explanations!

Why Doesn’t the Shiny Side of Aluminum Foil Make A Difference?

Yes, the shiny side is more reflective but reflective of what?

There are three basic ways heat can be transferred: conduction, convection, and radiation. Conduction is when heat is transferred through contact of one object with another hot object. This is what happens when we cook on the stove.

Convection is the transfer of heat by the physical movement of surrounding fluid (liquid or gas). Radiation is light waves, radio waves, microwaves, X-rays, etc. carrying heat energy from one surface to another.

Any object with a temperature above absolute zero emits infrared radiation. This means that the heated coils, sides, and racks in your oven are emitting infrared energy. Even the heated vessel and the heated food itself emits this energy.

However, when you cook food in an oven, the major source of cooking heat is convection. The hot air of the oven transfers heat to the food being cooked. Don’t be confused by “convection ovens.” All ovens use convection, convection ovens just use a fan to make the convection more efficient. Only a little of the heat transfer in an oven is through infrared radiation, which is invisible light rays.

A shiny surface should make no difference to convection but it will make a difference to radiation. Shiny surfaces reflect waves more than dull surfaces. The reason one side of the foil is more shiny than the other is because it is smoother and has less little imperfections: hills and valleys. So, the shiny surface of the foil should reflect more radiation than the dull surface, which will be better able to trap incoming waves rather than reflect them back. But it should not affect convection, the major source of heat transfer.

Aluminum foil: Shiny side and dull side. You can clearly see that the shiny side of the foil reflects more light (radiation) than the dull side. But, this should make little difference in a conventional oven, where the major source of heat transfer is convection

Consider a baked potato. When wrapping potatoes in aluminum foil for baking, you probably tend to place the dull side out. In reality, in the long length of time it takes to bake a potato, either side will work basically the same. The foil will be heated through convection and this energy will be transferred to the potato, and as the moisture in the potato heats up, the potato is cooked through steam.

Rather than which side is out, a bigger difference may be made by how tightly the potato is wrapped. Any air trapped in the aluminum foil pouch and surrounding the potato may act as an insulating barrier, slowing the transfer of heat. So, wrap your potatoes tightly before baking.

So, it is up to you which side of the aluminum foil goes up.

How is Aluminum Foil Made?

Since I already mentioned the manufacture of foil through the explanations given above, I may as well write a bit more about how foil is made.

The manufacture of aluminum foil is similar to making pasta at home. A large block of almost pure aluminum is rolled through giant steel rollers, several times, reducing the thickness of the aluminum block and spreading it out to make it longer. Lubricants are added to facilitate the operation. At each successive pass through the rollers, the thickness is reduced. The process is repeated until foil thickness is reached, and the large flat sheet is then split into the desired widths.

This may seem simple enough, but the actual process can be tricky. For example, as the aluminum is rolled out, it heats up. If it heats up too much, it can stick to the rollers, so the roller pressure must be carefully controlled.

Once the sheet of aluminum is 5mm thick, it must be rolled again in the cold-rolling stage. First, the sheet is spooled into a roll and then it is fed into the cold-rolling mill for the final stage of milling. It is at this point that the shiny and dull sides of the aluminum are created. Since the aluminum is now so thin, the tension needed to feed it through the cold rollers could easily break it. So, the sheet is doubled. The sides of the aluminum that come in contact with the steel rollers become more polished and shiny, and the sides of the aluminum that come in contact with itself become duller.

Tin Foil?

Foil is no longer made out of tin as it is more expensive and less durable than aluminum. However, the term tin foil is used for aluminum foil in many regions, including by some in the United States. The information on this page, then, applies to both aluminum foil and tin foil as both terms refer to the same product.

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