Seam sealing is one of those little things that some installers don’t understand makes a big difference in the performance of the carpet. I’m sure every one of us has seen a seam with edge ravel; usually this is because the seam has not been sealed or sealed improperly.

Over the years have I seen an increase in installers using seam sealer? Not as much as I had hoped. I just can’t figure out why ALL installers don’t use seam sealers when it ultimately could save them money from being responsible for a delamination or seam failure due to missing tufts. Carpet manufacturers require seam sealing, Adhesive manufacturers make seam sealer and tool manufacturers make tools for easier seam sealing, yet a very large number of installers don’t seal their seams.

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I hear the same lines I’ve heard for years: “They don’t pay me enough, it’s too messy, takes too long to dry, and the manufacturers should make carpet so it doesn’t delaminate or edge ravel.” And who is the ultimate loser? The end-user. The end-user never sees seam sealer but I can guarantee if they knew the carpet manufacturer required it they would most definitely want it. So who needs to take responsibility for sealing seams? The first and most important is the installer, the second is the retailer or workroom who hires the installers. Requiring your installers to follow manufacturer installation guidelines should be a mandatory requirement. It helps minimize your liability for the job, makes for a better installation, and most importantly results in a happy client.

Latex and acrylic. Through the years seam sealers have slowly evolved. On residential installations, latex is still used but you’re seeing a transition to the acrylic-based seam sealers which have a longer shelf life and clean up more easily with water while in a wet state. The latex is where many installers get into trouble. Latex doesn’t clean up well with water and if it penetrates the fibers, it’s very difficult to remove it. Installers who try to use a wet cloth find out all it does is smear and then makes a mess.

So what does an installer who doesn’t know how to use latex typically do if they spill latex on the surface of the fibers and then try to wipe it off? Scissors. They try to trim the surface of the carpet fibers only to find out it changes the color and texture of the carpet. The best thing to do if latex gets into the fibers is don’t touch it. Let it dry and then try to peel it off the fibers—once it’s dry it’s very flexible and should be able to be pulled from the fiber. If left on the surface, latex tends to yellow, stays slightly tacky and is a soil attractant which will lead to a complaint from the end-user; thus, the installer decides he or she is better off not sealing their seams because it’s “too messy.”

Acrylic on the other hand can be cleaned immediately with water and a clean white cloth. Acrylic dries clear so you don’t get the yellowing of latex. It also dries hard so if by chance a drop ends up on the surface pile, it will not be a soil attractant. If you’ve never sealed seams or are just not getting the hang of sealing seams, let’s look at the application methods and see if there is one here that will make it easier for you.

We’ve addressed the squeeze bottle application but let’s show you the proper way to use these types of bottles. If you’re an installer who started in the woven side of the industry you probably feel comfortable using your finger as a guide to applying seam sealer. Nowadays there are a couple of applicator tips that make it easier for the installer to apply seam sealer (photo 1). These tips work on both latex and acrylic. The blue one by Orcon has a deeper lip so that as you apply the seam sealer, the lip rides along the backside of the carpet giving you better control. The red tip by Beno J. Gundlach doesn’t have as deep of a lip. Now, which is better? Neither, it’s whatever each installer gets used to.

For thin backings I prefer the red tip, and for thick backings I don’t mind using the blue tip. Why? I personally have more control over the red tip with the amount of seam sealer that comes out. One thing to remember about sealing seams is you are not trying to apply seam sealer to the back of the carpet, which is referred to as buttering the back. All we are trying to do is seal the edge. Sealing the edge means sealing the primary and secondary backing together to prevent them from delaminating. So with that in mind, the red tip for me is easier to keep the seam sealer on the thinner-backed carpets because I can tilt the bottle at a higher angle to drive the seam sealer just onto the edge. If you use the blue tip, you’ll notice it’s more difficult to tilt the bottle at a higher angle because of the deeper lip, which allows more seam sealer to flow out and gets more on the backing.

Even though you may have sealed the seam, if it’s not dry, the moisture from the seam sealer may actually cause delamination or loss of bond when heat is applied and the moisture is driven into the backing.

There is nothing wrong with getting seam sealer on the backing as long as you let it dry before constructing the seam. If you don’t allow it to dry completely before constructing a seam with hot melt tape, you risk the chance of delamination of the backing and bond failure of the seam tape. Yes, I said that correctly. Even though you may have sealed the seam, if it’s not dry, the moisture from the seam sealer may actually cause delamination or loss of bond when heat is applied and the moisture is driven into the backing. Thermoplastic doesn’t like to stick to a wet surface and will have potential to fail. Try practicing on a scrap piece of carpet with edge sealing to make sure you are comfortable before attempting an actual installation. Also try putting a seam that has wet seam sealer on the backing, construct the seam and then pull it apart, and you’ll see what I mean.

Thermoplastic/hot melt. The next type of sealer is the thermoplastic/hot melt method. This utilizes a hot melt gun and hot melt glue sticks. There are a few different types of tips available on the market. Orcon and Traxx have similar tips and Gundlach also has a hot melt tip.

For those installers who have a difficult time using latex or acrylic in squeeze bottles, this might be a good solution. Installers will want a minimum 80- to 100-watt hot glue gun to maintain a constant flow as you seal the seam (photos 2 and 3). You’ll also want a black light to verify coverage of the hot melt on the edge if you’re just getting used to using this method (photo 4).

The two tips from Orcon and Traxx recommend the hot melt gun be horizontal to the seam and pushed along the seam edge. Each side of the seam must be sealed. The Gundlach hot melt gun with its tip is held upright and is pulled (photo5). Now, which glue stick to use? Each manufacturer has specific glue sticks for sealing seams, but aren’t all glue sticks the same? No, there are differences and knowing which does what is important.

Typically, glue sticks used for seam sealing have a lower melting point, so when the heat from the seam iron or thermoplastic comes into contact with the hot melt it will reactivate the hot melt on the edge and bond the two edges of carpet together. Do the two edges always bond? No, but as an installer, you did your due diligence in sealing the seam. So what happens if the two edges don’t bond? There is a potential for seam peaking because the seam can now hinge when a stretch is applied across the carpet. If the two edges were bonded together, hinging/seam peaking is minimized but there is still potential for seam profiling, from the profile of the seam tape.

Seam irons, weights and other tools. Now that we’ve properly sealed the seam what advancements have been made to seam irons or seam weights? The traditional hot melt seam iron is still the most common seaming tool used. Over the years it’s gone from a flat bottom to a grooved bottom or a combination of flat and grooved, to a deeper groove in the middle of the plate to allow more thermoplastic at the seam. The #893 seam weld iron from Taylor Tools, which channels thermoplastic to seal the edges of carpet at the same time the seam is constructed, is out in the market also.

Traxx has introduced a seam iron called the Blue Fin (photo 6). From the exterior it looks like your traditional iron but the difference is lurking inside the body. Inside the iron base is an internal heating element that is embedded in thermal gel, enabling faster and more even heating. The heat shield on this iron is tuned to reactivate Traxx seam welding sticks.

The Kool Glide tool (photo 7) I don’t even call an iron because it generates no heat, plus the fact it has multiple uses. This tool has been around now for several years and popular not only on the carpet side of the industry but has found a place in hardwood, resilient, laminate and tile installations. Radio waves react with a foil tape that has thermoplastic embedded on the foil that melts when the tool is activated. There is a seam tape designed for carpet and a utility tape designed for hard surface products. The nice thing about this tool is if you just happen to have an overlap or gap at the seam, you can reactivate the tape and make your correction. The manufacturer states you can reactivate the tape up to three times without compromising the integrity of the tape and adhesive.

I also want to briefly touch on carpet seam rollers. For hot melt seams, a smooth roller is recommended over a star-type of roller. A smooth roller does not distort the heat set yarns whereas a star roller has the potential to damage yarns.

Now let’s talk about seam weights (photo 8). If you’re still using your steel-bottom tool box or steel weight, which are heat conductive surfaces, you may want to change to another type of weight. Since the carpet fibers are heat set, if too much heat gets to the yarn, there is the potential for heat distortion of the yarn (photo 9). With today’s polyesters that we are all installing more of, it’s more important to use the right type of seam weight. Installers use wood- and plastic-based seam weights, but the latest is not a seam weight in the traditional sense.

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The Seamer Down Now (photo 10) uses a series of vents on the underside of the tool with a vacuum system on top to help draw the hotmelt into the backing of the carpet. This enables the seam to cool down quickly, creates a stronger bond of the thermoplastic to the backing of the carpet, and the installer has less down time waiting for the seams to cool. So have things improved over the years in regards to seam sealing and seaming tools? Yes. Now it’s up to installers to take advantage of the tools and be proud of their seams.