Countertops Magazine Archive

Adhesive Color Matching Issues Explained

Cartridge-based adhesives have the benefit of offering a repeatable, accurate color match to many surfaces (solid surface, quartz, natural stone, ceramic, etc.), without manually hand mixing and tinting of the adhesive, saving on labor and waste. High-quality adhesive companies cut and seam every sample it lists in its color charts (which could be more than 6,000 samples). During this process, if a small gap is left at one end of the seam, measurement of how the adhesive will appear can be made even in an imperfect joint. This mean that even though some companies supplying more than 300 adhesive colors, it is not impossible to achieve very accurate results.

As robust as the system is, there are circumstances where the color match or performance of the adhesive can be compromised. Color match issues can occur for several reasons. For example, manufactured sheet colors may drift or vary between dye lots, or operator error, surface contamination, off-ratio dispensing, exposure to extreme temperatures, exposure to UV light can occur, as well as instances of damaged or expired activator/adhesive.

This article will go over common color match issues and their likely causes. In general terms, always refer to a color match chart to ensure you are using the recommended colour. Check the condition of the adhesive, make sure the work surface is clean and at room temperature, then follow the recommended steps in each of the following sections.

Problem 1: Adhesive Doesn’t Match Sheet Color

Sheet good color drift: Quality adhesive manufactures measure colors annually and record digitally to ensure they stay the same from year to year. If a recommended adhesive does not provide the correct match for your application, the cause is usually a color drift in the sheet good. Sheet good suppliers use many natural minerals in their products, so it is difficult to keep consistency over time. Many, if not most, adhesive manufacturers endeavor to keep pace with these changes but as many variations are unplanned by the producer, it is not always possible. You should always feel free to send your adhesive supplier a sample of the material to rematch if necessary.

Storage: Although unlikely depending on the supplier, it is possible for an air bubble to be trapped in the activator or adhesive. Gases can also form in the activator if it is subjected to high temperatures during storage or shipping. These gases can result in off-ratio dispensing, which can affect the color of the cure. In the event that gas or an air bubble was trapped in the cartridge, upright storage will allow it to reach the top (outlet) of the cartridge to be eliminated during the initial purge (remember to purge with the cartridge pointing up).

For optimum shelf life and performance, store adhesive upright and away from direct sunlight. To further extend the shelf life, the adhesive may be stored in an air conditioned room or a fridge designed for the storage of flammable products.

Activator: Activator exposed to high temperatures during transport or storage will break down, discolor and lose strength; this will generally show up as a slow, uneven or incomplete cure. Activator stored correctly will last for a year or more but will lose reactivity over time (resulting in slower cure times). High temperature decomposition of the activator can also release gases into the activator component.

Air pockets may appear in the dispensed product and the compressibility of the gases may act like a spring compressing with each pull of the trigger, producing fluctuations in the dispensing rate, off- ratio (uneven cure) and drooling at the tip.

If you suspect a damaged activator, contact your supplier.

Problem 2: Adhesive is Discolored in Areas

Purging: After inspecting your cartridge and determining that it is ready for use, place it into the dispenser. Before attaching a mixing tip, it is recommended to purge a small amount of material to balance the two components. While you can do so through the tip, you run the risk of off-ratio mixing for the first portion of material and as a result you may end up with more activator or adhesive in your mix for the first few feet of bead you lay. This could cause product discoloration, a slower cure or even lack of curing.

Dispensing: Manual dispensing guns vary in quality, non-drip performance and mechanical advantage. Excessively high mechanical advantage dispensers may over pressurize the cartridge. Over pressurizing the cartridge can cause off-ratio dispensing and can lead to the material cross-contaminating at the nozzle of the cartridge. An off-ratio mix can cause adhesive color to shift during cure because of the presence of excess/insufficient curatives. This effect is especially pronounced on white adhesive colors. To minimize off-ratio dispensing, use the recommended static mixer and as little pressure as possible to dispense the adhesive at a reasonable rate. Author Recommendation: Use a dispenser with a non-drip feature with a minimum 0.050 in. of release (pull-back).

Ask your technical sales representative for dispensers approved for use with the adhesives and cartridges you are using. Use of non-approved dispensers can cause off ratio mixing (discoloration, uncured spots in the seam) and voids the manufacturer warranty.

Malfunctioning dispensers can cause uneven or incomplete adhesive cure. Some dispensing guns use plastic parts. They should be inspected for damage to the ratchet or brake mechanism and cracks or missing teeth on the plunger push rods. Damage to these parts will apply uneven pressure to the cartridge pistons producing an off-ratio mix.

• Check the condition of the dispenser, paying particular attention to the ratchet mechanism.
• Look for broken teeth, build-up of adhesive or play in the dispensing mechanism.
• Also look for loose, bent, misaligned or missing piston rod end discs.
• Check to see if the two piston rods are of equal length.
• Check to see if the dispenser body is bent, twisted or has adhesive build up that prevents the cartridge from accurately aligning to the piston rod travel direction.
• Test the dispenser. Before placing a cartridge in the dispenser, watch the action of the piston rods when the trigger is pulled to see if the non-drip feature retracts the piston rods between strokes.
• Place a cartridge in the dispenser and balance the pistons (purge adhesive until both components are visible before attaching the mixing tip to ensure both components are flowing). Attach the mixing tip then purge a small amount of adhesive (1 teaspoon). Release the trigger and see if the adhesive stops flowing or if it continues to drool out of the outlet. If drooling continues for more than a few seconds, the adhesive dispensers’ non-drip function is not working properly.

The triggering action used with manual dispensers is an important technique to ensure an even cure.

• Apply smooth even strokes; maintain constant feed and pressure using the full stroke of the trigger.
• To minimize off-ratio dispensing, use as little pressure as possible to dispense the adhesive and maintain a constant forward motion of the cartridge pistons.
• Failure to prevent excessive drooling caused by poorly designed or defective dispensers can cause uneven cure and cross-contamination leading to blocked cartridge outlets.

Cold Adhesive:

• Some adhesive components become thicker at low temperatures and may not mix as well. Thickened material creates higher pressure in the cartridge and tip, which will flex the cartridge wall and will produce an off-ratio mix.
• Adhesive stored in the fridge or a cold shop should be allowed to return to room temperature before use.
• If you re-warm adhesive, make sure the cartridge outlet plug is in place (failure to do so may cause cross-contamination).
• A mixing tip left on the cartridge can allow expanding adhesive to back flow into the activator chamber and result in a plugged cartridge.
• Never warm adhesive or activator above 110 degrees F. The activator will be damaged.

Cold Sheet Material: Bonding sheet goods that have been stored below normal room temperature will cause the adhesive to cure slowly in the joint. Fabricating with cold sheet goods may prevent a full cure from ever developing as the monomer may evaporate before cross linking can occur. Conversely, fabricating with hot surfaces may also cause problems with cure color and bond strength.

Uncured adhesive will rapidly deteriorate leading to weak and discolored joints.

Problem 3: Adhesive Full Bead is Discolored

Surface Preparation:

• For best results, surfaces need to be dry before applying adhesive. Porous surfaces (like granite, limestone and marble) need extra attention to make sure internal moisture has been evaporated. Surfaces also need to be free of dust/dirt and degreased before applying adhesive. Solvents that evaporate and don't leave a residue are best. Acetone or alcohol work well.

• Lamination strips and the backs of the sheets must be clean, dry and unpolished. The adhesive needs some texture to bond to the surface. The degree of preparation required varies widely depending on the type of stone and the processing it has received prior to the fabrication process. If the stone is rough but the surface is full of dried slurry from the cutting process, the adhesive will be unable to make full contact with the surface resulting in a weak bond. If the surface of the stone has been calibrated, is fairly smooth and is contaminant free, then a cleaning with acetone or alcohol is sufficient.

Conclusion

The above tips and techniques should help maximize the benefits of using cartridge-based adhesive on deck seams, laminated or mitered edges. They will help achieve a seamless look with minimum labor and waste. While not everyone uses cartridge-based adhesives, with the growing number of surfacing materials compounded by the continuous increases in the number of colors of these materials, it is a method well worth examining for maintaining an efficientand smooth fabrication operation.

About the Author

Jean Poisson is general manager of Integra Adhesives Inc. He can be reached via www.integra-adhesives.com; North American toll free phone: (888) 862-6665; international phone: (604) 850-1321; or by email at [email protected].