by Larkin Greene
The increased moisture and lower temperatures associated with Winter and Spring present significant challenges to successful adhesive applications. Adhesives prefer warm and dry, along with clean. Anyone who regularly picks up a horse’s foot knows that none of those characteristics happen without effort.
The Effects of Cold
Vettec products perform optimally when used between 60 and 80F, in other words, room temperature. When temperatures fall below that optimum range, adhesives become more viscous, harder to dispense, and take longer to set. Both methacrylates and urethanes produce an exothermic cycle that is critical to their final set. Colder temperatures inhibit that heat cycle; if the adhesive cannot generate that heat, the set will be softer, and the bond less reliable. While many users are familiar with the need to warm up the adhesive, it’s also important to warm any surface it touches, including mix tips, any glued-on device, and especially, the surface of the foot itself. If you forget to warm a surface, applying heat after the adhesive is on the foot can help, but does not guarantee success because the exothermic cycle is a chemical reaction formulated into the adhesive. For temperatures below freezing, a heated workspace is essential to achieving predictable results.
Keeping materials warm is easy enough; most keep them in the cab of the truck, in an insulated container, or home-made hot box that contains a light bulb or warming pads. The worst thing one can do is store them in the rig in cold weather, then try to warm them up prior to using them. It takes time to warm up cold material, and it is best done slowly. It’s easy to heat up the plastic cartridge, but it takes a while for warmth to penetrate throughout the material inside the cartridge. Best practices would dictate not letting the material get cold in the first place; however, if quick warming is necessary, putting cartridges on the dashboard with the defroster running works well, or perhaps on the floorboards with the heater on. Some have even reported success putting them in the engine compartment for a while after arriving at the barn.
Within the preferred temperature range, SuperFast sets in 30 seconds for non-weight bearing applications, and requires a minimum of 2.5 minutes before bearing weight on bottom applications. Adhere sets in 45-60 seconds for non-weight bearing applications, and needs 3.5 minutes minimum before bearing weight in direct glue-on applications, five minutes would be better.
The Effects of Excess Moisture
Excessive moisture is the most common cause of adhesive failure in equine applications. The inability to get the foot dry enough remains a challenge for many hoof care practitioners. Fortunately, there are tools and techniques that allow us to conquer this problem. Some methods work better than others. For example, a hair dryer is louder and less effective at drying a surface than a heat gun. A heat gun is much quieter and more effective, held a few inches away, and kept in motion. Another tool equal to or superior to a heat gun, is a hand-held propane torch with a soft flame. The torch has the advantage of not requiring power, is also quiet, and produces great results if the same technique is applied: inches away and in constant motion.
Adding a moisture meter to your adhesive tool box is the best way to know that surfaces are actually dry enough for bonding. Typically, the moisture meter must read below 10% for successful bonding, though single digits is desirable, and very attainable. Once the foot surface is dry enough, the adhesive should be introduced in as short a time as possible for best results.
Effects of Excess Moisture After Bonding
If all protocols for proper bonding are followed at the time of application, excess moisture afterward is less detrimental, but can still lead to failure. We know that horse’s feet swell when the ground is wet, and shrink when it dries out. If that change happens during the weeks when an adhesive is in place, you can expect it to be a contributing factor in the failure of that application. Frequent sessions at the wash rack, standing in an irrigated pasture, muddy paddock, or any other saturation conditions can contribute to shorter longevity, or early failure. No bond can withstand immersion for any length of time beyond passing through a creek.
Following these guidelines for storage and handling of adhesives can dramatically improve success rates, and reduce the level of frustration users often experience when weather turns cold and wet.