In the beginning, there was pin tape. This type of tape was used in doorways when hand sewing was the method used for constructing seams in woven carpet. The tape had small metal barbs/ “pins” in the strips every few inches. The pins ran across the width of the tape and a scrim was applied over the barbed strips (Photo 1). Installers would layout a hall area and room, match patterns at the doorways, apply a liberal amount of latex to the pin tape, place the two carpet edges into the tape, and roll with what was, and is commonly known as a “porcupine” roller (Photo 2). The roller has very sharp needle like points, these points penetrate the backing of the woven carpet and help draw the latex into the backing for a better bond.
Once the latex was dry, the installer would stretch in the carpet. Prior to pin tape in a multiple room installation, the installer would lay out the hallway piece or pieces, lay out the room piece inside the room, align, and place reference marks on the backing of the patterns at the doorways. Following these steps, the installer would then roll up the room piece towards the seam and take the roll out of the room, and place it into the hallway. With the flap of the roll lying with the backing facing up, the hallway piece was folded back so that the two backings were once again aligned at the reference marks. The installer then used a needle and thread to hand-sew the seam; once this was done, latex was liberally applied at the seam for reinforcement and allowed to dry. Once the seam was dry, the installer would carefully fold the roll back into the room, unroll, and then install. Quite a bit of work just to construct one doorway seam; just think of the amount of time it would take if there were multiple doorway seams. Thus came the invention of pin tape to make the installer’s work much easier, especially for handling of the carpet. Pin tape is no longer manufactured and those that still hand sew keep a close eye on any pin tape they may have; in fact, if any of you installers out there have any extra, feel free to contact me!
One thing that I’ve noticed as I travel throughout the United States and abroad conducting training and certifications is the amount of different hot melt tapes that are currently being used. My last unofficial count put the number at more than 130 different tapes. Now I know that some may be private labeled but nonetheless the installer is inundated with choices. One manufacturer I spoke too stated that they had a minimum of 41 different tapes. The thermoplastic beads in seam tapes range from 2 3/4 inches in width, up to 6 inches in width (Photos 3 and 4).
There is a hot melt seam tape that has Stabilizing Tempered Steel Bars (Photos 5a and 5b) and one that uses radio wave technology instead of a heat source to melt the thermoplastic (Photo 6). So, why are there so many different tapes?
With the amount of different carpet backings, the need for certain types of formulations to create a strong enough bond to the backing and the seam tape has manufacturers each creating their own formulations for what they feel works successfully with the different types of backings. Some even use cinnamon, vanilla or other scents, to create a pleasant scent when the thermoplastic melts.
You have the standard polypropylene backings, backings with a fleece, and certain woven backings. Urethane backings require a hot melt that is compatible to the backing; a urethane hot melt is used for these types of backings. A regular thermoplastic may hold temporarily but will not have a permanent bond. There are double stick tapes designed specifically for double stick installations with pressure sensitive adhesive on the back of the tape to adhere to the cushion. A utility tape using radio wave technology for installation of hard surface products such as wood, tile, and laminate (Photo 6, left side).
There are even designer tapes that are used in area rug fabrication. This type of tape has a removable carrier paper. The tape is rolled out under the seam; the seam is constructed with a traditional hot melt seam iron. Once the seam has cooled, the paper carrier is removed simply by peeling it off the back of the seam tape (Photo 7). This enables the rug fabricator to overlap tape for design work without the worry of too much build up of seam tape or the silicone backed seam tapes not sticking to each other.
Photo 8 is what installers used, and still use, before silicone was applied to the backside of the tape to prevent the tape from sticking to the cushion. If the installer didn’t use toilet tissue, the tape would bond to the cushion and prevent the carpet from stretching. Toilet tissue is also used for hand-sewn woven carpets. Once latex is applied to the seam, and if there are multiple seams in a room, the installer places tissue on the seam covering the still wet latex, folds the carpet panel back in place so that they can continue hand sewing seams without having to wait for latex to dry for each seam. The tissue paper keeps the latex and seam from sticking to the cushion. The tissue paper works well for seams and well, you know, the real intent it was designed for.
At each training/certification event that I attend, the question is asked, how many installers use one tape? The majority of installers will raise their hands, when asked the type and why they use it, the response is because there is a lot of adhesive and it bonds quickly to the carpet backing. Is this a good thing? Yes and no, the more adhesive that is on the tape, the more the tape has the potential for seam profiling. Seam profiling is different than seam peaking. Seam peaking occurs because the carpet is bonded at the base where it comes into contact with the seam tape but not the entire area between the primary and secondary backing. When there is tension placed on the seam, where the carpet is held in place by the seam tape the tension is equal to the backing of the carpet. Where there is no bond between the secondary and primary backing, the stress from stretching tends to pull this area up into a slight peak. Seam profiling is where, in a stretch-in type of installation, the tension that is placed at the seam forces the tape up, the bottom of the tape must come into alignment with the carpet backing. This means that whatever the thickness and width of the seam tape, that thickness and width will telegraph or “profile” at the surface of the carpet. A “low” profile seam tape, one which has less hot melt and a thinner paper backing is more suitable where seam profiling is more apparent such as areas of natural light striking across the seam when it can’t be avoided. Some installers will argue that you need a lot of hot melt for a strong seam; not if the seam is constructed properly. First, when preparing the seam, if top row cutting is recommended by the manufacturer, do so, as the cut will follow the natural construction of the carpet by following down a row. This will eliminate cutting any face fibers. Photo 9 shows a few types of top row cutters and a loop pile cutter, far left. Second, make sure to seal all seams, this means both cut pile and loop pile type carpets. Many installers state that they only seal Berber, or loop pile products but not cut pile carpet. Unless the manufacturer states otherwise, ALL carpets need to be edge sealed. Either latex, acrylic, or hot melt are acceptable as seam sealers.
Make sure to seal both edges of the carpet seam, not just one side, (you know who you are). Third, construct seams on a hard surface. A piece of 1/4 inch plywood or masonite 10 inches wide by 3 to 4 feet wide is ideal. This enables the two carpets at the seam to be flat when placed into the hot melt and rolled, which brings us to the type of roller. A smooth roller should be used on cut pile carpet and a star type roller used on looped pile carpet (Photo 10). A non-heat conducting seam weight finishes the proper seaming process. Follow the proper procedures and you’ll have a well constructed professional seam. As for seam tape that you use, don’t limit your selection to only a single tape; different tapes will give different appearances. Ever have a carpet that is the same color and style, two different installers prepare their seams the same and yet one installer’s seam appears to be less visible? It could be the difference in the “tale of the tapes.”