The devil lives in the data - Woodshop News

The devil lives in the data

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Tell the truth now. Have you ever used a new product, perhaps a stain, filler, glaze or sealer, without reading the instructions? Have you assumed that since you’ve been spraying lacquer for 20 years and you’ve had no problems for the last 18, that you’ve got it all figured out and don’t need no stinkin’ directions? Has that ever backfired?

There have been a lot of changes in the finishing world in the last, well, maybe a hundred or more years, and more rapidly in the last 10. Many of them are clearly beneficial, some are a pain without showing clear improvement in performance and most require some adaptation of our thinking and our technique.

Unless you are working directly with a manufacturer’s rep or a really informed distributor, you won’t be advised of many important changes in the product you are buying and, even if you are, that rep or distributor might not be as diligent as you wish. There could be unstated and unwarranted assumptions that you know everything you need to know to profitably use the product.

When I was first working at Mohawk Finishing Products in the early 1980s, I quickly learned that many of the customers’ problems with finishing products involved them not reading or understanding the use instructions on the can and there was little else to inform them.

Today, with all the regulatory mandates concerning what has to be on the can (sometimes in several different languages), there’s just not enough room for the details you need. Here’s where the product data sheet comes in.

In black and white

Virtually all the manufacturers of professional finishing products make available to their customers and distributors, in hard copy or, increasingly, online, product data sheets, technical data sheets or product use instructions. These contain information such as:

Description of the product, guiding you in determining suitability of the product to your needs; physical properties such as chemical resistance; types of applications and working properties such as pot life and reduction. You don’t want to buy five gallons of a product at a great price if it has shelf life of six months and you only need two gallons or a straight lacquer with little moisture resistance for a bathroom.

The PDS gives you that shelf life information, as well as other pros and cons of that product. Sales and marketing personnel might be interested to find that a particular product is recommended for use in kitchens and baths because of enhanced resistance to moisture, food products and household cleaning products.

A small finishing shop could be attracted to a ready-to-spray formulation that reduces the need to store more solvents, while a busy custom cabinet shop might need a fast-dry formula to speed production.

Technical characteristics can include gloss measurements, solids content (note difference between solid content by volume and weight), viscosity, recommended film thickness per coat, spreading rate (coverage) dry times to touch, handle, sand, recoat and ship. Also directions for incorporating additives, like reducer, retarder, flow enhancer, bubble breaker, flatting paste, colorants, catalysts or hardeners and limitations on types of additives that are acceptable.

It is almost always safer to use a single manufacturer’s product line of topcoats, sealers, reducers and additives than to experiment with different manufacturer’s products, risking incompatibility. Many coatings need a certain minimum total dry film build to achieve the desired performance and must not exceed a maximum total dry film thickness in order to avoid cracking and checking.

Specifications can include general prep instructions and typical finishing schedule. These specifications are the result of laboratory testing and field experience with specific schedules designed to perform as desired.

Application directions can be very simple or comprehensive, according to the manufacturer’s practices. One very good example includes catalyzation, reduction, temperature, viscosity and humidity parameters, and typical setups for air and fluid pressures and cap and tip setups for conventional spray, airless, air assisted airless and HVLP systems.

Some materials will not work well with some specific spray systems. Improper catalyzation can result in incomplete or slow curing. Over-reduction can cause runs and increase the cost of materials used. Under-reduction can cause poor finish quality.

Keep it handy

Finishing technicians should be very familiar with the PDS for the materials they are using and be alert for changes. The PDS should be stored in a convenient location for quick access. Management should monitor adherence to the approved application protocol and exceptions should be allowed only after thoughtful consideration and testing.

Performance tests on the materials, especially for kitchen and bath fixtures and commercial applications, are becoming more important. Moisture resistance, resistance to household chemicals, cleaners, abrasion, or food items might be required for certifications, such as the AWI or KCMA. Marketing and sales personnel and literature use this data to promote the proper product for certain uses.

This data on a PDS is seen as more credible than vague hyperbole on a sell sheet and is more likely to be supported by actual test data according to standards such as the American National Standards Institute), the American Society for Testing and Materials) and many others.

Storage temperature, important with solvent base coatings, can be critical with waterbornes; too low a storage temperature can alter the performance of many waterbornes and too high a temperature can shorten the shelf life. While solvent-borne finishes can tolerate cooler temperatures, cold storage risks spraying with coatings below the recommended temperature for application, raising the viscosity of the coating. Applicators are often tempted to try to compensate by adding reducer or retarder, which can slow drying and affect the production schedule, as well as adding the cost of the additive to the operation. Storage on a cold concrete floor, even if the ambient temperature is moderate, can result in lost time and energy in bringing the coating to application temperature. 

Your coatings vendor has a vested interest in the quality and economy of the product you produce. He provides the product data sheet as a tool to help you reliably maximize that quality and economy by training technicians, guiding designers and engineers, purchasing and marketing, toward that end. 

Greg Williams, formerly senior touchup and finishing instructor for Mohawk Finishing Products, is now a freelance instructor and consultant.

This article originally appeared in the October 2016 issue.

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