How to Block Light in Silicone Tubing

Silicone is a class of durable, flexible material that has a number of uses. Silicone tubing is frequently used in automobiles, aquariums, medical devices, scientific research and in various chemical processes. It's favored for these tasks because its silicon-oxygen polymer backbone makes it more durable, flexible and resistant to heat and chemicals than most organic plastics, which have a carbon backbone. However, silicone is often translucent, meaning light from the surrounding environment can affect the contents of the tubing. In some circumstances, it may be necessary to make the tubing impermeable to light.

Things You'll Need

• Aluminum foil
• Electrical tape or thermal tape
• Paint thinner
• High-temperature spray paint or latex paint

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Instructions

Choose the Proper Tubing

• 1

  Determine the proper size and thickness for the tubing. If you are working with material that will be under any pressure, make sure the silicone tubing is rated for at least 1200 psi. The outer diameter of the tube should be around twice the inner diameter of the tube unless you will be pumping fluids at a very slow rate. For example, tubing with an inner diameter of 1/8 inch should be at least 1/4 inch wide on the outside.

• 2

  Make sure oxidation is not a problem. Silicone tubing is much more permeable to gases than most plastic tubing. This means oxygen can get through the tube with relative ease and may react with certain fluids that you are working with. In other words, your problem may be oxygen rather than light.

  If oxidation is a problem, you may want to look into temperature resistant plastics instead of silicone. For instance, sulfone-based plastic tubing is frequently temperature resistant up to 400 degrees Fahrenheit and is much less permeable than silicone is. They are also considerably more expensive.

  Check to see if your chemical oxidizes easily by looking at its material safety data sheet (MSDS). If you don't have an MSDS, you can obtain one from your chemical vendor. These sheets are frequently available for free online. If the flammability or reactivity indices on the MSDS are listed as 2 or above, there is a good chance that your chemical oxidizes easily. In this case, you should look into a chemical- and heat-resistant plastic polymer for your tubing.

  Also note that silicone is not recommended for acids and organic solvents, which can damage the tubing much more rapidly than with other types of tubing.

• 3

  Choose silicone tubing that will block most of the light.

  Get the most opaque silicone tubing you can buy. Silicone coolant tubing is opaque and may suit your needs without any additional modification. Most silicone tubing is not opaque, but comes with varying degrees of color and translucence. If you buy tubing that has a deep color and is not see-through, it will block most incoming light. You can also get peroxide-cured, UV-resistant silicone tubing that will block highly-energetic UV rays that can damage the liquid in the tube.

  The blue silicone tubing frequently used in the air lines of aquariums blocks over 90 percent of the incoming visible and UV light and is relatively inexpensive. This is a good start to blocking the light in your silicone tube.

Cover the Tube to Block Incoming Light

• 4

  Wrap one or two layers of aluminum foil around the tube. For a 1/4-inch-wide tube, cut a rectangular strip of aluminum foil about 2 inches wide and 12 inches long and carefully wrap it around the tube. For thinner or thicker tube diameters, you may have to adjust the width of the strip. After you're done wrapping the foil around, check the foil covering for gaps.

  This is the easiest way to block essentially all incoming light and should work in situations where even small amounts of light can damage the contents of the tube. Unfortunately, aluminum foil is somewhat delicate and will not work for long in tubing that is exposed to considerable movement or chafing.

• 5

  Hook the tubing to your apparatus. For instance, in an aquarium, you would now place the tubing on the adaptors for your pumps and filters. If possible, do this before you start pumping liquid through the system. Take note of any small gaps in the aluminum foil at the ends of the tubing or along its length after you've put it in place.

• 6

  Electrical tape can be purchased in most hardware stores.

  Wrap tape around the foil. This will serve to hold it in place and make the foil layer more durable. Use black electrical tape if the tube won't be exposed to temperatures over 175 degrees Fahrenheit. If the tube may be exposed to higher temperatures, use thermal tape instead.

  Wrap the tape around the ends of the foil and any bends. You don't have to cover the foil completely with the tape. Just wrap the tape around the foil-wrapped tube two to three times every four to six inches.

• 7

  Make sure this method will work for you. This will work in the great majority of cases where you need to make silicone tubing light resistant. In the remainder of cases, usually situations where the tube will be subject to frequent vibration or chafing, you should try painting the tube.

Paint the Silicone Tube

• 8

  Carefully apply paint thinner to the silicone tube. Pour a little paint thinner onto a cloth or paper towel and wipe it over the surface of the tube. This will alter the surface texture and plasticity of the tube so you can apply paint to it.

• 9

  Apply two layers of black latex paint to the tube. Paint the first layer and allow the tube to thoroughly dry before painting on the second layer. The coloration of the tube should appear even, and you shouldn't be able to see the original color of the tube beneath the paint.

  Latex paint is elastic and won't crack easily, though it may degrade eventually if exposed to the outside environment. It will also provide a barrier that will reduce the amount of gas exchange between the inside of your silicone tubing and the outside environment.

• 10

  Heat-resistant spray paint is often used in engines and other high-heat applications.

  Spray two or three coats of heat-resistant spray paint on the tube if it will be exposed to high temperatures (over 160 degrees Fahrenheit) that can melt latex paint. Let the tube fully dry between coats. When you're done painting the tube, you shouldn't be able to see any of the original coloration beneath the paint. If you see any spots or thin areas, apply extra paint to them.

• 11

  Check the paint-coated tube after it's been in use for a short time to make sure cracks or seams aren't developing in the paint. This can sometimes happen when the tube moves around a lot or the liquid inside is subject to pressure, which causes the tube to expand and contract.