Achieving Great Performance with Low VOC Gloss Paints

Gloss paint is one characteristic used to capture the appearance of paint. We are all aware of the various sheen levels used in paint applications:

Flat Paints: dull, porous; used primarily on broad wall (drywall) and ceiling applications. Hides surface imperfections.

Eggshell/Satin: more reflective than flat paints and can impart some warmth and depth to a room

SemiGloss: excellent in higher demanding areas including kitchen and bath, kids room paint. Delivers better stain and adhesion

Gloss Paints: used primarily on trim and doors

Two key components, binder and pigment, dictate the overall level of gloss in a paint – the higher the pigment level, the less glossy the finish.

When we consider resistance properties, appearance and uniformity, and the adhesion performance on the widely varying substrates used today, the demands on gloss paints are perhaps more stringent than other classes captured above.

In the past, formulators employed their expertise to enable good enamel like performance from waterbased gloss paints. When compared to other types of paints, the gloss binders were harder. The right additives were used to ensure proper flow and the right solvents were used to maximize open time and workability of the paint. With increasing environmental regulations, both suppliers and formulators face new challenges to ensure acceptable performance of gloss paints. VOC (Volatile Organic Compounds) emissions for gloss paints have shifted to as low as 50 g/l in California (South Coast) – while there is continuing downward pressure in other areas (the VOC limit currently is at 250 g/l). The trend to lower VOC specification has placed increasing challenges and opportunities on both the suppliers and formulators.

As depicted below, top quality 100% Acrylic Gloss paints delivers exceptional durability advantage in exterior applications (when compared to oil based paints). This advantage in UV resistance and gloss retention is well accepted by formulators and applicators today.

What is less readily acceptable is the broad utility of low VOC waterbased gloss paints in interior applications. Some believe that alkyd paints deliver unmatched flow and adhesion and hardness development in interior applications. As VOC regulations tighten, the debate has shifted – waterbased technology is more desirable. One key question addressed in this newsletter is whether one can sufficiently optimize the appearance characteristics to enable waterbased technology to displace alkyds or oilbased paints. Specifically, we will look at Open Time and Flow with todays top quality 100% Acrylic gloss paints.

The most significant issues with applying waterbased gloss paints are highlighted in the picture below.

The good news is that today’s top quality waterbased paints can be formulated to overcome these difficiencies as shown below:

How is this accomplished?

Flow/Sag Balance:
Most of us prefer a smooth, rich finish (free of brush marks) when painting doors and trims. Formulators use today’s modern synthetic rheology modifiers to deliver the final smooth and rich look in transform this into.

Open Time and Repairability:
Traditional latex paints are poorer than alkyds for this property. That is, latex paints dry faster, resulting in poorer wet edge – shorter time until the extreme edge of a drying film of paint can be reworked with a fresh coat of paint. Poor wet edge generally leads to poor flow/brush-marks as a line of dried paint is visible under the rebrushed area. Despite this inherent deficiency, top quality 100% Acrylic Paints are optimized to deliver outstanding flow and sag balance provided some simple guidelines are followed : http://www.paintquality.com/diy/content/howtopaint.htm#doors See recommendations for Six Panel Door at end of newsletter.

In general, the best practice is to avoid immediate repairs of brush and coverage defects -- best to allow paint to dry and then sand and touch-up defect areas.

Brush Drag – Use of Quality Tools:
There is little question that skill is a key component to delivering a quality finish. We have shown that different applicators get different results when brushing the same paint. Note too that paint manufacturers can tune the rheology to impact the brush drag and loading on the brush. A recent study with PQI and a leading brush manufacturer highlighted that in addition to individual skill and technique, that the composition and design of the brush also impacts the final finish. The quality of the brush will determine the amount of paint picked up and transferred to the surface. For starters, PQI recommends a top quality brush (with longer bristles; and with ends tapered and flagged).

Applicator Guidelines:

The idea is to keep a wet edge while doing all stiles and rails simultaneously. The painter must work quickly and carefully, being sure to keep brush or roller adequately filled, and using just two or three brush strokes per application: A. Paint each panel using brush or roller and     brush then use either a roller or brush to: B. Paint the top rail C. Keeping a wet edge, paint all stiles down     to just onto the next rail; then D. Paint the next rail, keeping a wet edge E. Then continue downward on each stile,     stopping in the next rail F. Etc. G. Etc. H. Finish by doing the bottom rail.