Here’s a scenario known to frustrate all parties on a paint project—and although this incident involved new construction, the same problem can surface on a maintenance repaint:
- The architect designed a school—the latest of many done by the firm.
- The specification writer prepared the detailed spec.
- The colour consultant released the color schedules.
- The general contractor had the project nearing completion.
- The paint contractor prepared to start application.
- The paint store tinted the paint order to the selected colours.
- The specified paint was applied.
- The students came to school.
- The surface marked excessively, prompting students to further mar the finish.
- The school board demanded answers.
- What happened? Who is responsible?
Not My Fault
The architect and the specification writer are approached first. They respond that the specified semi-gloss high-performance architectural latex (a product approved under MPI) had been used with considerable success on school after school after school with no such problem. In fact, MPI’s High Performance Architectural Latex standards (MPI #138, #139, #140, and #141) are designed to be its highest-performing interior latex standards.
The painting contractor is approached next. He responds that he followed the spec and purchased the specified semi-gloss latex coating, tinted to the colour selected.
The paint manufacturer is up next. He insists that the proper material was supplied and tinted with universal colourants (which are now increasingly zero VOC) to the colour chip selected by the colour consultant. The paint batch was checked at the lab and found to meet spec. A drawdown was made, and the colour was found to be within the acceptable tolerance range.
The Challenges of Deep Tones
So what happened?
The key to the answer is that the semi-gloss latex required the addition of about 15 ounces of universal colourants to the base to achieve the desired colour.
Too much of most universal or glycol-based colourants can have an adverse effect on a paint's properties, including a reduction in abrasion and mar resistance; a drop in sheen from semi-gloss to low gloss; delayed drying time (sometimes twice as long as expected); and poor hiding that can mean extra coats.
So, using deep colours can affect paint performance as well as the project’s ability to meet schedule, budget and aesthetic requirements. Since deep hues are in vogue with today’s design community, here are guidelines for successfully specifying and applying these materials.
How Tinting Affects Paint Performance
Deep colours affect paint performance in two ways:
- Colour pigments are softer than white pigments; and
- In-store colourant systems can change the characteristics of the paint.
Colour v. White Pigments
A good white paint typically has greater resistance to abrasion and marking than deep tints and accent colours do, because the clear bases used for deep colours lack the titanium dioxide (TiO2) that makes white paint white.
But TiO2 is not just a whitener. It’s harder than most colour pigments. That hardness makes a big difference in the paint’s resistance to impact and marking. So a paint film loaded with TiO2 will be more robust than one loaded with soft colour pigments.
The Nature of In-Store Colourants
The vast majority of colourants that a store uses to tint your paint consist of powdered pigment dispersed in a liquid that contains glycols and surfactants (even with zero-VOC systems). So adding substantial quantities of material (e.g. 15 ounces per gallon) that will become a permanent part of the paint film can, for all practical purposes, change the paint formulation.
One readily noticeable difference may be a substantial increase in dry time, due to all of that non-drying glycol/surfactant being added to the can. (Note: This is not an issue if the paint product uses a resin-based colourant system.)
One alternative is to use factory-made colors. Back in the day, it was common for paint stores to carry “stock” colours. A customer could walk in and find black, red, or other basic shades right on the shelf in cans that came straight from the factory.
When deep colours are produced at the factory, the colourants are added as dry powder milled directly into the paint; no glycol-containing dispersion vehicle is required. In addition, the paint manufacturer can optimize the formula by adding additives and extenders to strengthen the film and increase hiding.
So a paint company’s formulation for factory-produced “black interior latex” will always offer superior hiding and performance than a store making black paint by adding tint to a clear base.
The industrial maintenance paint industry still produces plenty of coloured paints right in the factory. But not the architectural coatings market: We now expect paint suppliers to offer countless custom colours, so stores are understandably reluctant to have factory-tinted stock on hand.
In this inspector’s experience, if you order exceedingly large quantities of paint, you can get the product factory-tinted—but orders of less than 300 gallons or so will end up getting tinted in the store.
Matching Another Manufacturer’s Colour
The problem can be exacerbated when a paint store is asked to match a colour chip from a different manufacturer.
We realize that this happens all the time, but be advised that a paint company designs its bases and tint systems to produce its own colour system—not that of a competitor. Trying to match another company’s deep colours may require adding excessive tint base, leading to all the problems described above: a drop in sheen, delayed dry times, weak hiding power, and reduced resistance to burnishing and marking.
Most store reps running the tint machines are aware that adding excessive colourant may degrade the paint's properties and still not precisely match the competitor’s chip. However, when an anxious customer asks for more colourant because the shade “isn’t quite right,” the rep understandably finds it difficult to say no, and the customer generally gets his way.
The nature of the pigment can also affect performance. For example, some coluor systems create darker browns by adding yellows in the tinting process. On a building exterior, southern exposure walls that are exposed to more UV light may exhibit excessive fading.
Other colour systems, however, may obtain the same dark brown with alternative colour mixtures or pigments, and the result is a very colourfast finish.
Tips for Applying Deep Tones
A well-meaning contractor may believe that deep- and accent-coloured paints require four, five or even six coats to achieve hiding. Here are options to avoid this trap.
- Ask if the paint supplier can recommend a primer or intermediate coat that will provide optimal hiding underneath the colour specified.
- Learn which undercoat colours enhance the hiding power of which topcoat colours. For example, if a yellow topcoat is specified, the area should first be undercoated with an absolute pure white. Avoid any shadowing or gray tone, which can telescope through the yellow. Red finishes are best undercoated with a brownish red, which has more robust hiding power than pure red.
- Follow the manufacturer’s instructions on dry time between coats. Applying a new coat before the previous coat has completely cured can compromise hiding power. Picture this: You’re rolling out a brilliant, deep red, but you allow only “dry to touch” time before applying the next coat. The new coat will re-wet and soften the previous one, causing it to get picked back up in the roller, so you end up removing some of the previous coat while applying the next. That's not conducive to good hiding!
- Some paint manufacturers now offer colour tint bases in basic colours (e.g. red, yellow, and blue). When a store tint machine starts with a base that has the initial pigmentation built into the base, fewer ounces of colourant will be needed to achieve the desired colour.
Repainting Non-Uniform Surfaces
Sometimes we see repaint projects where the surface is already discoloured with spots in a different colour (for example, a green wall is touched up with blotches of yellow patching compound).
The owner now wants a color change to orange. If the painter tries to apply the orange intermediate and topcoat directly over this wall, the result will be a washed-out orange over the yellow patching material, and a muddy orange over the green areas.
It could take many more (nine or 10?!) finish coats to achieve a uniform appearance on this wall than either the painter or facility manager had planned. And even then, the underlying difference in colour may still telegraph through. The solution is to first apply a suitable primer/undercoat to create an absolutely even all-over colour, using the guidelines above.
Tips for Specifying Deep Colours
We often see specifications that call for one coat of primer, plus one or two coats of intermediate/topcoat. However, as we've discussed, this may fall far short of what’s needed to achieve suitable hiding and the desired finish with deep tints and accent colours.
So we make sure our specs also include the phrase, “Deep and accent clear-base colors may require 1-2 more coats to achieve the proper hide.”
If the right undercoat/primer is strategically chosen to complement the intermediate and topcoat, and the undercoat/primer is carefully applied to achieve a totally uniform appearance, suitable hiding may be achieved with two coats of primer and two coats of finish.
The key to success is to minimize surprises. Do a test patch first. The time to realize you have a problem should be after the second coat, not after the sixth.
Know the potential impact of your colour choice before the project starts.
Editor's Note: This article was written by PQA Inspector Dave Lick and is reprinted with permission from the MPI (Master Painters Institute) newsletter. MPI content describes best practices for commercial, institutional, and light industrial painting.