Seam scorching happens more often with the new resilient materials featuring PUR coatings. When an installer heat welds these new materials/coatings, he will need to play close attention to both the heat welder heat setting and the speed of travel.

This month’s mail bag includes diverse questions about primers and underlayments, the use of full spread for loose-lay or modified loose-lay materials, and scorching during heat welding. It also covers the cause of cracks when flash coving, yellowing in new linoleum, cleaning a seam before sealing, causes of vct tile shrinkage, benefits of sealing vct tile, and rolling materials installed with epoxy adhesives. If you have any questions for Ray for use in a future column, send them to:

Q: When going over a gypsum underlayment are you supposed to use a primer?
Most gypsum underlayment manufacturers recommend applying a PVA primer just prior to the application of an adhesive. The primer hardens the surface and reduces the dusting at the surface. The primer will also enhance the adhesive’s bond to the underlayment.

Q: When should I full spread loose-lay and modified loose-lay materials?
A lot of installers do not feel comfortable installing materials that are not fully adhered to the substrate. The fact is these materials work well in a modified loose-lay. The exception is with heavy foot traffic and rolling loads. There are some adhesive manufacturers producing releasable pressure sensitive adhesive for these situations.

Special care must be taken to not allow the resilient material to scorch. A new type weld nozzle can help stop the scorching, as well.

Q: Why does it seem that the materials that require heat welding are more prone to scorching than the older materials? 
The newer materials have a PUR coating applied to the surface to make the material easier to maintain. When an installer heat welds these new materials/coatings, he will need to play close attention to both the heat welder heat setting and the speed of travel. Special care must be taken to not allow the material to scorch. A new type weld nozzle can help stop the scorching, as well.

Q: In flash coving of sheet vinyl, what causes the cracking to occur at the juncture of the floor and wall, where the cove stick is used?
There are several possible answers: the cove stick is not secured properly or there is a gap between the floor and wall bigger than the cove stick allowing the cove stick to slide back under the wallboard. Additionally, it is possible the flooring material was not fit tightly enough into the cove stick, leaving a gap between the material and the cove stick. Installers must fit the material firmly into the cove stick, as it is a labor-intensive repair.

Q: Why does linoleum appear to have a yellowish cast when first taken out of the roll?
When linoleum is in its final curing stages of production it is hung in ovens (drying rooms) for several weeks. During this process a yellowish film may develop on the surface of the product. This film is common on all linoleum products and is part of the normal curing process of the linseed oil found in linoleum.

This yellowing goes by a few different terms: stove yellowing, seasoning bloom, drying room film – all are used to describe the same phenomenon that affects all linoleum. This yellowing will disappear, depending upon the amount of natural light. Yellowing can be gone in as little as a few hours to a few days. This is why it is common for the new material not to match the old sample.

Overstripping the finish of a vct tile floor can cause major damage to the floor. Make sure to follow proper maintenance procedures outlined by the manufacturer.

Q: What is the best method to remove the soil from a seam that got dirty prior to the application of the seam treatment?
First take the backside of a knife blade, something that has a flat edge, and remove as much of the soil as possible. Then take a toothbrush and some white toothpaste and scrub the remainder of the soil out. Toothpaste is a mild cleaner abrasive and will do a good job. Avoid any solvents that may drive the soil into the material or destroy the adhesive beneath the seam. Be sure to clean the seam thoroughly with a clean, damp, white rag.  

Q: What is the best type of integral (flash coved) corner to use on a commercial installation of non-patterned sheet vinyl, wrapped (v-plug) or mitered (boot)?
I prefer the wrapped corner. I think it is easier to put on, it will take more abuse from buffer machines and everyday use, it stays on better than a mitered corner and with no seam at the outside corner or on the floor, it looks better. Not all installers are well versed on wrapped corners. The wrapped corner does not work very well on patterned materials.       

Q: What causes the tile joints in a VCT tile installation to shrink uniformly?
There are several possible causes for this to occur. Consider these: The VCT tile was not stored in an area under normal environmental conditions. The VCT tile was subjected to a damp environment prior to installation. The substrate was too wet to install over at the time of installation. There was no temperature control in the facility at the time of installation or immediately afterward before the tile adhesive was set. The floor maintenance was started before the tile adhesive was set. There is a moisture problem and the adhesive did not set properly.

Q: What is your opinion about the use of a sealer instead of a floor stripper for VCT tile?
I think a sealer is a great idea. A floor sealer is a high alkaline-resistant floor polish. Once a VCT tile installation is complete and the adhesive cured, (approximately five days) a couple of coats of floor sealer topped with a couple coats of polish will help protect the VCT tile and the tile adhesive for alkaline-based cleaners and strippers. There are a lot of installations that are compromised by improper maintenance procedures. The use of a stripper too soon will allow the adhesive to be attacked by the floor stripper.

Q: Why is it necessary to roll the material that is installed with epoxy adhesives multiple times?
Epoxy adhesives with a high solids content do not have an initial tack. With a high solids content, there is little or no shrinkage when the adhesive sets. This means the adhesive just goes from a liquid state to a solid. Since there is no tack and no shrinkage of the adhesive to draw the material down, the material must be rolled into the adhesive. The material will resist staying in the adhesive because of roll curl, substrate undulation and trapped air. So rerolling the material is extremely important.

Failure to reroll an area that has come loose will result in a bubble that is difficult to repair because the adhesive cannot be reactivated. The normal rolling procedure with epoxy adhesives is immediately after the material is placed into the adhesive, again in one-half to one hour and a final rolling after about three hours. Many installers use masking tape on the floor to indicate the number of times each area of the floor has been rolled and rerolled.