Precatalyzed Coatings — as Easy as 1-2-3
A look at some of the characteristics of ‘precats,’ as well as tips for using these popular coatings with maximum success.
By Mac Simmons
New advances in the technology of chemistry have brought about changes and unprecedented breakthroughs in many of the new coatings that are now available in the finishing field. These new coatings are being introduced at such a rapid rate, it appears that every six months a new coating is “making the rounds,” and some coatings that have been used for years are either being replaced or newly improved. Yet there appears to be a market for all coatings, because sales of coatings increase each year. This includes more and more catalyzed coatings, popular because they are very durable and have a high degree of chemical resistance.
This article will discuss catalyzed and precatalyzed coatings, focusing on their features and characteristics and explaining how they work. It is important to understand all materials, as they play a significant part in the overall finishing process. Having this knowledge will help you avoid any of the problems that can and do occur in finishing.
Precatalyzed coatings are now being used a great deal in woodworking, and there are many reasons why they are becoming more popular at this time. In this coating, pre-measured amounts of a catalyst and reducers are added during the manufacturing process and not during the finishing procedure, as is the case with two-component post-catalyzed coating systems. Because this coating is precatalyzed and pre-reduced, it is ready for use. There is no mixing or measuring of either a catalyst or reducer to add.
In addition, two-component post-catalyzed coatings have a pot life of only hours after they have been catalyzed. After that, the mixed coatings may become unusable, because once the catalyst has been added to the coating, it will begin a chemical reaction to begin cross linking (defined later). Precatalyzed coatings do not have this short pot life. What is not used in the spray gun cut or in the spray pots in one day can be poured back into the container for future use or left in the spray pots for spraying the next day or a week later. The “precat” will not harden in either the cup or the spray pot. (However, all spray guns should be thoroughly cleaned after using any finishing material.)
The way catalyzed systems work, the addition of the catalyst first causes an action and then a reaction of the molecules in the catalyst and the chemical base of the coating. This causes the chemical molecules to “cross link” which, simply stated, is a process of the molecules to overlap other molecules which are near or next to them. In some catalyzed coatings, there are different degrees in the cross linking process. If too much of the catalyst is added to the coatings, it will cause problems, like the coatings actually over-hardening. Eventually this condition may cause the coatings to crack, or cause them to lose their adhesion to the substrate. During the cross linking process, this may actually shrink the coatings, as it tightens the molecules over a period of time.
Most catalysts are usually acids, and it is important to follow the manufacturer’s directions and use the correct amounts of catalyst and coating. Likewise, if the manufacturer’s instructions recommend that only three coats be applied, then that should be the maximum amount used. Having too many coats containing too much acid can overheat the coatings, causing a faster curing. This can affect not only the recoating of the finish by over-using the catalyst, but also, if you apply too many coats, it will cause premature curing that will continue on after the finish is completed on the project. This may lead to further problems in the future.
One of the disadvantages of precatalyzed coatings is that they generally are not as durable or as chemical-resistant as two-component post-catalyzed coatings. They also take a longer time to achieve their maximum hardness and chemical resistance, which is approximately 30 days after they are applied.
This is because there is only a small quantity of the catalyst added to these coatings. If the manufacturer added more of the catalyst, the coating would cure much faster and the shelf life would be even shorter. (Most precats have a product shelf lie of about six months. This could be even shorter in a shop or storage cabinet where the temperature is very high, as heat will also accelerate the curing of these coatings.)
So it is better to buy only what will be needed for a month or two and to reorder as it is used. (Always write the dates you receive coatings on each container and use the older containers first.)
When choosing a coating, it is important to use only those products that are completely compatible with every catalyzed coating you will be using. This would include any primers, sealers, paste wood fillers, stains, shading stains, toners, glazes and materials such as additives that may have to be used with these coatings. It is always best to buy your coatings and materials from the same manufacturer, as he will know what is compatible with each of his products or can recommend what is compatible.
Never assume that you can use or mix other products with a catalyzed coating, as you may have a delayed reaction that does not show up during the finishing process but becomes a problem at a later time. Whenever you buy a coating, you should ask what you can use with it and what should not be used.
Since all post-catalyzed and precatalyzed coatings are not the same, do not expect that you will be able to achieve the same results, performance or chemical resistance from them — trying to compare a catalyzed lacquer to a catalyzed polyester is like comparing pine to oak. Do not expect the same results or performance in their service over the years. Also, do not choose coatings that “out price” your work — you may be able to use another coating that has some of the same characteristics but sells for a lower price and also gives a good, durable and chemical-resistant finish.
Just as you should follow manufacturers’ directions in mixing precats and selecting compatible materials, you also should follow suppliers’ application instructions carefully.
Most of the precatalyzed coatings are similar in their application to the other conventional coatings — they sand easily, rub out well and can be compounded in about 48 hours after they are coated (under most conditions). They also are repairable with most conventional repair products and tech
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