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Tech Facts Volume 5

Tech Facts Vol. 5 – Clear Vinyl

Clear vinyl, known as “isinglass” in the marine industry, has a multiplicity of uses.  One of the most common….the “clear plastic windows” found in convertible tops, Jeep tops and boat enclosures.

Like much of extensive technical and applications data available on the 303® website, this detailed information is manufacturer-supplied and written in layman’s language for our valued enthusiast customers. 


History:  Flexible vinyl is a product that was developed shortly before World War II.  Commercial development was stopped during the war effort, then resumed in the early 1950’s.

Clear vinyl is available today in two general types known in the industry as “rolled goods” and “sheet goods” with sheet goods (also known as “pressed poly”) being the higher quality.


Resin is the basic ingredient.  The raw materials used to make resin are chlorine and ethylene.

PlasticizersPlasticizers are used to give flexibility to the vinyl material.  Plasticizers are oils. Soybean oil is often used as a plasticizer ingredient.

Heat stabilizers protect the material from thermal breakdown during manufacturing.  Typical stabilizers are metal compounds, which early on included some heavy metals.  Due to health concerns, heavy metals are no longer used.

Lubricants Lubricants allow the molten material to flow and not stick to the hot surfaces of the metal processing equipment.  Lubricants are fatty or waxy materials.  Lubricants also allow easier fabrication of the finished product.

UV or Light Stabilizers
 – absorb ultraviolet light, giving material a longer outdoor life.  
Pigments – small amounts of blue or gray pigment are used as coloring agents.  If no color is added, the material has an undesirable yellow appearance.
Low Temperature Plasticizers – added to the plasticizer mix to give vinyl greater flexibility at low temperatures.  In a warmer environment, this plasticizer will cause “hazing” on the surface of the vinyl.
Mildew Inhibitors – used to control the growth of molds and mildews.


For the production of clear vinyls (up to and including .020” thick), machinery called a “calendar” is used.  The first process in the calendaring operation is the mixing and blending of ingredients.  The material is then passed to a worm-driven gear extruder where it is heated to the correct temperature.  After being pushed through a “screen pack” (to filter contaminants) at the end of the extruder, the material – in the form of a heavy hot log – moves on to begin the process of being flattened.  The still-hot-and-soft material then passes through several series of rollers that flatten, shape, control temperature, polish and gauge the thickness of the material.  The winder at the end of the line is equipped with cutters for trimming the width.  The winder is tensioned to control for minimal shrink of the product.  A high pressure roller set up will squeeze out air and water marks. 

At this point the clear vinyl is referred to as rolled goods and is available to the market. Goods are rolled with a layer of paper, the rolls stored and shipped standing up.

Pressed Poly (sheet goods): For materials with a thickness of .030” or .040”, layers of calendared vinyl (rolled goods) are put through a laminator under heat and pressure to bond the plies together.  Pressed poly sheets are stored and shipped on edge with protective paper between each sheet.


Lay Flat – Not laying flat usually indicate uneven thickness across the roll width

Gels and Streaks – The compound or mix of formula ingredients did not completely dissolve

Air Bubbles – Final wind-up rollers have not pressed all the air out of the rolls.

Watermarks – Can indicate a wind-up problem or, if a “water bath” is used, can indicate water impurities.

Excess Shrinkage – Normally 1-2% should be allowed for shrinkage in the length direction of the roll.

Hazing – The chemical mix of ingredients is not stable enough for the environment.  Hazing appears on the surface of the vinyl as a slightly oily film.


Because it is very pliable, vinyl can be scratched easily and caution needs to be used when working with or cleaning the material.

Cleaning: Clear vinyl should be cleaned regularly to remove dirt (and salt water deposits). Abrasive cleaners should not be used.  Avoid detergents. Manufacturers recommend soap and warm water.  Any of 303®’s cleaners can be used safely instead of soap and water, or when soap and water alone is not sufficient to do the job. Rinse the material first to remove any solids which might scratch the vinyl.  Make the cleaning solution with soap or the 303® cleaner with warm water.  Saturate a soft wash mitt with the cleaning solution and wash the material. Afterward rinse with clear water.  Dry with a clean, non-abrasive, absorbent cloth.

Storage: Vinyl windows and curtains should not be folded or stored for an extended period of time when damp or wet.

Sun exposure:  Though clear vinyl and other vinyls and plastic used outdoors have UV stabilizers added during the manufacturing process, all UV stabilizers are sacrificial…meaning they are used up by sun exposure.  For UV protection, 303® A. Protectant can’t be beat.  

A 303® tip for older clear vinyl:  Some older clear vinyl that has become oxidized and slightly scratched can be “restored” (meaning the appearance and most of the clarity can be restored). Then use 303® Aerospace Protectant™ to protect against UV and extend its life.  If, however, the clear vinyl has begun to yellow and/or embrittle, it’s too late.  (Note: the first place you’ll notice yellowing and/or embrittlement on clear vinyl is at the bottom of  where it turns toward horizontal…this is where it gets the most UV).

1) To remove oxidation and minor scratches, purchase one of the fine-abrasive plastic polishes made for this purpose.  3M and other manufacturers make such products.  The particular product may be labeled “polish” or “cleaner”, but what you want is the one that has a fine-abrasive polish and which leaves no coating or residue.  

Following the manufacturer’s directions, polish away the oxidation and small scratches.  When finished, you will see a dramatic improvement in clarity. 

2) Use 303® A. Protectant to “perfect” the clarity.  The specialized 303® polymer does this by making the light go straight through the almost invisible, tiny scratches which are still there causing the light to bend slightly, reducing the clarity. 

To apply: Spray on 303®, wipe COMPLETELY dry. Using a second clean, absorbent, non-abrasive DRY cloth to remove any excess 303® and polish to a high gloss.  The improved clarity will be immediately apparent.

303®’s invisible, non-oily, protective finish is EXTREMELY repellent to dust, dirt, fingerprints, etc.  Your treated vinyl will stay cleaner longer and clean up easier the next time you clean it.  Periodic cleaning/re-treating with 303® A. Protectant maintains this clarity and repellency, and is the best UV protection there is.