Prepping Acrylic Sheet Prior to Decoration

Photo by Andrey Bayda / Shutterstock.com

Whether you are painting acrylic sheet, digitally printing it or decorating it with applied vinyl graphics, proper prior surface preparation will prevent adhesion problems. While acrylic is similar to other plastic, the procedure used in cleaning its surface is often different.  Because acrylic is very susceptible to chemical stresses, always follow the guidelines and the recommendations in this article.

Removing the Surface Protection Masking. 

Acrylic sheet is typically protected with either a paper or a low density polyethylene surface protection masking.  Obviously, you must remove the masking before decorating the sheet.  To minimize the amount of contamination that can collect on the surface of the sheet and to protect it from accidental scratching, don’t remove the masking until you are ready to use it. 

Surface protection masking on plastic sheet can often become difficult to remove, especially if the plastic sheet has been stored for a long time and has been subjected to the pressure of sheets stacked one on top of another.  Under no circumstance should you store masked acrylic sheet outside.  The effects of sunlight on the masking can crystallize its adhesive, often making its removal impossible.  

If the masking gets wet, a milky white residue might remain on the sheet.  Sometimes you can remove this residue by merely wiping the surface with a soft damp rag.  If that doesn’t work, try to clean the residue with Rapidtac’s Rapid Prep. Then, thoroughly rinse and dry the surface after cleaning.

If the paper masking is next to impossible to remove, do not soak the paper with water or application fluid.  This trick may work when removing stubborn application tape from applied vinyl graphics, but when removing masking from plastic sheet, the likely result is some type of adhesive residue. 

Instead, soak the protective paper masking with a solvent to loosen the grip of the masking’s adhesive. Be sure to only use a solvent approved by the plastic sheet manufacturer.  After waiting for at least ten minutes for the solvent to work its magic, attempt to remove the masking. If at first you don’t succeed in this procedure, try, try again.

In some cases, after removing the protective paper masking, an adhesive residue remains.  In many cases, you can roll the adhesive off of the surface with the pressure of your thumb.  If this doesn’t work, saturate a clean cloth with naphtha and rub it on the adhesive.  After the adhesive is removed, wash the surface with detergent and clean warm water.  As an alternative to naphtha, try cleaning with isopropyl alcohol (IPA) and rinsing with clean water.

Static Electricity. 

Most plastics accumulate a static electric charge on the surface of the sheet.  When you tear the masking from the sheet, even more static is generated.  If you don’t neutralize this charge, the static will attract dust and dirt like a magnet, which can show up in your paint job. Spray painting a surface with a static charge can also result in a blotchy finish, which will stick out like the proverbial sore thumb, when the signface is illuminated.  

Static electricity creates problems in decorating with most any kind of plastic and acrylic is no exception.  Electric charges on the face of the acrylic sheet can cause an uneven deposit of paint. In screen printing, it can cause spider webbing.  Static charges can also create a magnetic attraction between an acrylic sheet and vinyl graphics, complicating vinyl application. 

Maintaining relative humidity
at 60% to 70% can greatly
reduce static related problems.

One way to get static under control is to control your shop environment.  Maintaining relative humidity at 60% to 70% can greatly reduce static related problems.

Sign makers use a couple different techniques to kill or neutralize the static charge.  One common practice is to wipe the surface with a damp, lint-free rag.  Others wipe the surface with a damp chamois moistened with a solution of water and isopropyl alcohol at a ratio of 9:1. Dry any residual moisture with a hot-air gun.  Another practice is to kill the charge with an ionizing air gun. Do not use anti-static cleaners or dryer sheets, which can contaminant the substrate, potentially causing paint adhesion problems.

For additional information on neutralizing static and the problems it causes, see my article Problems with Static Electricity.

Surface Preparation. 

After removing the masking, it’s time to prep the sheet.  Do not use window cleaners, or strong solvent to clean the sheet.  Cleaning the surface with a dry rag is also verboten.  Dry rags potentially could scratch the plastic as well as generate a static charge.

Regardless of how you decorate acrylic, you must clean any contamination off of the surface.  Failure to properly prep the sheet prior to processing often results in graphics failure. These failures include poor paint or ink adhesion, inconsistent coatings and peeling vinyl films.

While we all know that you can make an ass of you and me, when you assume, we should always assume that every substrate has some surface contamination and requires cleaning. In the graphics field, this is the universal exception to the “never assume” rule.

In prepping acrylic prior to decoration, follow the manufacturer’s instructions explicitly. Some cleaners are appropriate for cleaning acrylic, but many are not.

Do not clean acrylic with solvents such a toluene, xylene or lacquer thinner, which can craze the sheet. Be very careful in using any solvent stronger than alcohol for cleaning.  Strong solvents will subject plastic sheet to stresses that often result in crazing and eventually cracking. If the surface has grease or tar, try naphtha or kerosene to remove it. If you have to use one of these stronger solvents, be sure that the sheet is completely dry before painting.

NOTE: When subjected to physical or chemical stresses, many thermoplastics, such as acrylics will craze, which looks like a very fine network of tiny cracks.  The crazed area of the normally water clear acrylic will also whiten. The reason is that the crazes scatter light.

Crazing is not the same thing as a crack, in which the sheet has a full-blown fracture.  Crazed acrylic can support a load. A fractured or cracked sheet will not.  As a crazed sheet is subjected to additional stresses, the crazing can propagate into a bona fide genuine crack.   

In cleaning acrylic sheet, many veteran sign painters recommend the following procedure. Fill a bucket with clean water and a mild, non-abrasive detergent.  If you use a dish washing detergent as a cleaner, do not use the type with hand moisturizers. These lotions will contaminate the substrate, which could cause paint adhesion problems.  After soaking a cellulose sponge in the water-detergent mixture and lightly wringing out the sponge, wipe the surface down.  Then finally wipe the surface with a sponge dampened in clean water. This process accomplishes two ends, the static is neutralized and the surface of the sheet is absolutely clean.  Do not commercial anti-static cleaners, which can leave a residue and interfere with good paint adhesion.

A word of caution: Because some plastics are susceptible to scratching, clean it carefully. Do not clean acrylic with strong solvents, such as lacquer thinner, toluene and acetone. Cleaning with solvents, even mild ones, such as isopropyl alcohol may craze the surface of the acrylic sheet. Avoid using brushes, squeegees or other cleaning devices that could scratch the sheet’s surface. After washing the surface, rinse with clean water and dry with a soft cloth to prevent water spotting.

You can clean most contaminants washing with dishwashing detergent and water and rinsing with clean water.  This may not clean any oily contamination, such as skin oils.  If you need to prep a surface with isopropyl alcohol (IPA) or stronger solvents such as naphtha, kerosene or mineral spirits to remove grease or oily residue, always follow the solvent cleaning by washing the surface with detergent and water, and rinsing with clean water.

Vinyl Application Videos

Squeegee Technique. Nothing is more basic in vinyl application than the squeegee. But some squeegees work better than others. And there are right ways and wrong ways to use this simple tool. This video clip reviews squeegee selection, squeegee care and squeegee technique. Click to Link

Wet Applications. Dry applications are typically recommended for most vinyl applications. For those exceptions to the rule, this instructional video explains the right way to perform a wet application. Click to Link

Application of Window Graphics. Installing vinyl graphics on glass can be challenging, because the adhesive aggressively grabs onto this high energy surface. Repositioning graphics on window is generally difficult, if not impossible. This instructional video explains how to dry apply window graphics right the first time. It also describes the necessary steps required for surface preparation. Click to Link

Transferring Frosted Window Graphics Films.  Because frosted window films are highly textured, transferring cut vinyl graphics can be problematic. This video provides direction in selection of the right application tape and how to apply these films quickly, easily and without problems. Click to Link

3-Step Surface Prep. This instructional video describes how to properly clean the surface of a vehicle before applying pressure sensitive vinyl graphics to a trailer or doing a full wrap of a car or van. This three step surface prep involves detergent washing, solvent cleaning and a final wipe down with IPA. Click to Link

Vinyl Application Over Rivets. Applying vinyl graphics on vehicle surfaces with rivets is challenging for most sign makers. Vinyl failures to these surfaces are all too common. This video demonstrates some tips and procedures, used by professional decal installers, which will make these demanding applications easier and more trouble-free.  Click to Link

Vinyl Application to Corrugations. Learn how to apply vinyl graphics to corrugations in a relaxed state. Forcing films into the valleys of corrugations puts too much mechanical stress on the film. Sooner or later, the vinyl will lift or tent in valleys. Click to Link

Applying Air Egress Vinyls. Vinyl films with air egress release liners have almost eliminated bubbles and wrinkles from applied graphics. Air egress release liners with their highly textured surface structure are problematic. Not much will stick to these liners other than the vinyl film. At RTape our best premask solution for air egress liners is a special Conform® tape called 4761RLA. Click to Link

About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.  Vinyl Sign Techniques is available at sign supply distributors and at Amazon. 

Slides of Jim's Artwork

© 2016 Jim Hingst