Making PVC dimensional signs

It warps and it has no rigidity. It swells if it gets too hot. You can bend strips of it in half, though sometimes a little bend is all it takes to make it break. What made me think I could tame this wild beast? How did PVC sheeting, a material that once seemed to have no apparent sign-making qualities, become the most commonly used material in my shop?

Well, I was running out of options to replace my material of choice for dimensional signs, which was redwood. Plus, I’ve always believed that an open mind will lead you to places that could never be imagined. That approach led me to give expanded PVC board a try as a suitable material to fabricate durable dimensional signs.

In the beginning

Sign making in the ’80s was simple and overhead was low. In the early ’80s, I made dimensional signs using an opaque projector, lettering brushes, enamel paint and lots of redwood. Little did I know big changes were coming. Soon the Gerber Signmaker was helping handle the routine work. The durability of acrylic latex paint improved. The local lumberyard had all the wood you needed.

In the early ’90s, Classic Sign & Mirror consumed an average of two thousand board feet of redwood every three months. We began buying directly from mills in the west. I added computer-aided sign design and our first router table. My opaque projector was starting to gather dust.

Right here a great ending would be “…and Mike and his family lived happily ever after.” But that’s for fairy tales. A major problem was about to raise its ugly head. It soon became apparent that redwood and related woods were in short supply and maybe unavailable altogether. What was a wood sign maker to do?

The search for a substitute

First we tried medium-density fiberboard. In dry climates, or for interior signs, it works fine. In humid Florida it absorbs moisture and swells with disastrous results. Then high-density urethane board came along. It was more costly than redwood, but with the Grain Fraim [Sign Arts Products, 800-338-4499, www.signfoam.com] it could be sandblasted to resemble wood grain. It also required less labor during fabrication than wood. Its shortcomings, though, are that it lacks rigidity and usually needs additional support when used for long signs or freestanding signs. When bumped, it dents because its surface isn’t as hard as redwood.

One day, in desperation, I looked hard at PVC sheeting; a material that had been getting limited use in our shop for years. Because PVC board doesn’t cut well with saws, we used it only for rectangular sign panels done with vinyl letters. It did, however, cut well on our Gerber Sabre router, and we had made some cutout PVC letters. But it was plastic, yech! What was a quality sign maker to do?

First, I had to get over the idea that plastic meant low quality. Today’s plastics are strong, durable and cost effective. Even so, I couldn’t help looking at our first dimensional PVC sign and thinking that I had reached an all-time low in my career. The sign was very heavy and lacked rigidity. It even made creaking and squeaking sounds when you moved it around. To top it off, the finish was not the greatest and we had problems applying it. I didn’t like the rippled look of its surface.

The fine line

We began testing and researching to identify PVC board’s strengths and weaknesses. Along the way we discovered how fine the line is between being clever and being stupid. Our early efforts showed little promise. Then I looked to my roots in aviation technology; specifically, a lightweight construction technique used to construct rigid aircraft bodies called Monocoque construction.

In aircraft construction the aluminum skin is attached to lightweight ribs. When all the ribs are connected to and covered by the skin, the result is a strong, lightweight shape. Most aluminum aircraft bodies are fabricated using this technique. I felt I could get reliable results using PVC sheeting and a similar technique.

Pros and cons

The advantages of PVC sheeting are that it is available in many thicknesses and there are many suppliers. It’s easily cut and shaped with a router or carved with chisels. It’s water resistant and holds up well unpainted outdoors. It holds a painted finish very well, too.

At first look, PVC board’s disadvantages are enough to make you think twice. It expands and contracts a lot. Because it absorbs heat unevenly, it can become distorted. Cracks can form from sharp edges and spread quickly. It’s heavy and has uneven thickness. It’s available in varying quality, and surface distortion can be pronounced on low-cost product. It gets easily charged with static electricity, which can cause painting problems.

Overcoming the disadvantages

Expansion and contraction ratio: Everything expands and contracts with temperature. Even high-density urethane will change in length by up to 1⁄8 in. over a 100-degree temperature spread. PVC is a bit livelier at three eighths of an inch over eight feet. So if you fabricate 8-ft. PVC board at 50-degrees temperature, it will grow three sixteenths longer at 100 degrees and three sixteenths shorter at zero degrees. This is a lot of change.

The most common way to handle this is to place the sign in a rigid frame with room to move. This may not be convenient and the frame is a perfect place for mildew to form. The best way—and the secret to success with PVC board—is to create a hollow box as the main sign body.

By moving the faces out away from each other, you create a structure that is lighter and more rigid. Any change in shape is absorbed by the wall structure that connects the two faces to each other. Any minor warping is so small that you’d need to lay a straight edge on the surface to see it. This approach also addresses the weight issue, by resulting in a lighter sign.

Uneven thickness: I use Sintra brand PVC board because it seems to have the most even finish. The surface seems to vary a plus or minus .015 of an inch in the thicker sheets, sometimes more near the edges of the sheet.

This is hard to notice and only becomes a problem when V-carving letters under six inches into the surface with our router. Then the surface variation can cause the small letters to be distorted.

Because of this, we do a lot of inlaid, raised prismatic letters and applied carved panels cut in the thinner material where the distortion is less. This technique adds some material and labor cost to the construction. This increase is offset by the fact that parts can be painted separately by less experienced workers, usually by spray painting. No need to hand paint sections or mess with masks.

Cracking: The potential for cracking is greatly reduced by removing sharp edges as you do when working with acrylic or glass. By slightly rounding sharp edges, you eliminate the stress areas that are the starting point for cracks.

Painting your work: When I first started working with PVC board, all the manufacturers recommended finishing with vinyl inks or catalyzed paint—no enamels or acrylic latex. I felt that since acrylic latex paint is really only vinyl, just like PVC board, it should work. We did some unscientific testing and away we went, fingers crossed all the way. We found that acrylic latex forms a mechanical bond. Scuffing the surface with fine sandpaper or a 3M Scotch-Brite™ pad gives the paint something to grip. Wiping the surface with a damp rag before painting eliminates any static.

Bonding and fastening PVC board: The obvious choice to bond PVC to itself is PVC pipe cement. It welds the material together for a permanent structural bond. For some applications, this is the only thing to use. To apply letters, panels or any nonstructural parts I found that polyurethane adhesive sealant makes an excellent adhesive. (I use Sonneborn NP1.) It sticks well to just about any surface. This isn’t always a good thing, like when you get it on your hands or where you don’t want it on the sign. It also remains pliable for years and unlike silicone, it can be painted. It also comes in quite a few colors. The drawback is that it takes a few days to fully cure.

Caution: PVC has a class II fire rating. This means that it will burn but will not sustain a flame burning on its own. The danger is in the fumes created when it is burned by an outside source. If you char PVC, it emits chlorine gas, which is extremely dangerous. It’s okay to heat it up a little, just don’t melt it. There is a familiar aroma when cutting PVC, like the smell of those inflatable swim toys you get for kids. Don’t let that smell make you all warm and fuzzy because we really don’t know the long-term effects. Provide proper ventilation.

My experiences using PVC board to construct dimensional signs have led me to products that I can deliver with confidence. Through trial and error, I have achieved the success I was looking for. This doesn’t mean that PVC board is the answer for every sign we make. I like working with a wide variety of materials, but I find myself looking more and more for ways to include PVC board because I like the durable, attractive results.

Mike Sheehan’s shop, Classic Sign & Mirror, is in Pensacola, Florida.

This appeared in the May/June 2003 issue of SignCraft.

 

Routed 24-by-60-in. Sintra PVC sign, finished in copper LuminOre with a natural patina. The corkscrew on the hanger was created uncoiled using ArtCam software in 3⁄4-in. PVC board heated until softened, formed into a spiral and allowed to cool.

Routed 48-by-96-in. hollow sign with PVC decorations mounted on 6-by-6-in. wooden posts. With darker background colors you have to allow a little more room for expansion and contraction.”

Routed 60-by-128-in. PVC sign mounted on PVC posts. This sign flexes in heavy wind. If you want to make PVC structures, you have to believe the old proverb: ‘What doesn’t bend, breaks.’ This sign has been up for several years and is holding up great.

Routed 12-by-24-in. hollow PVC sign with 1⁄4-in. faces. The hanger is laminated PVC board—no metal at all. This 38-by-78-in. sign is constructed of two laminated layers of 1⁄4-and 3⁄4-in. PVC board with inlaid SignFoam III letters and scroll. The letters and scrolls were created in ArtCam 3D software.

This 38-by-78-in. sign is constructed of two laminated layers of 1⁄4- and 3⁄4-in. PVC board with inlaid SignFoam III HDU letters and scroll. The letters and scrolls were created in ArtCam 3D software.

Each 3⁄4-in. PVC lens frames on these 24-by-48-in. eyeglasses was cut on our Gerber Sabre router as a front and back half, then laminated with PVC cement. The nose bridge is made of 1⁄2-in.-thick front and back cutouts laminated over a brass rod.

This 3-by-7-ft. sign is constructed of 11⁄2-in. laminated PVC board with 1-in. inlaid SignFoam high-density urethane letters, finished with acrylic paint.

This 36-by-54-in. sign is all PVC board. The faces are 4 in. apart with two 4-in. PVC post covers between them. The faces are connected by a strip of 1⁄4-in. PVC board that fits into a groove in the back of each face. The carved border was created in 3⁄8-in. PVC board using ArtCAM software. The inlaid letters are finished in copper LuminOre that is finished with a natural green patina.

Routed 24-in.-diameter sign of 3⁄4-in. PVC board, finished with acrylic automotive paint. The herons are carved SignFoam III high-density urethane board inlaid into the background.

The Bakery panels are curved around a rib on each side of this routed hollow PVC board sign. The bread and muffins are carved high-density urethane board and the cookies are castings of real cookies.

The two 1⁄2-in. PVC panels of this 24-by-48-in. sign are laminated together with the 1⁄2-in.-sq. steel hanger enclosed in between. The faces use inlaid letters and 1⁄2-in. beveled panels. The scroll on the hanger unit is PVC board painted to match the steel.

Routed 24-by-72-in. panel of 1-in. PVC board with inlaid PVC letters, attached to 4-in. PVC post covers. Make sure that the posts have a slightly loose fit to allow for expansion and contraction.

The two routed faces on this 21-by-108-in. sign are bonded to 1⁄4-in. PVC letters glued on. The sign is enclosed with 1⁄4-in. PVC strips that fit into grooves cut into the back of each sign face.

The curved main panel on this 48-by-120-in. sign is supported by laminated curved ribs. The 5-in. PVC posts pass through the end of the ribs. Curving a panel makes it more stable and adds a look not often seen.