A colorful, eco-friendly coating with historic durability
Milk paint’s durability, ease of application, and visual characteristics have made it a colorful go-to finish for ages. Made popular for its use in venerated furniture styles such as Colonial and Shaker, it has withstood the test of time. Contemporary makers have embraced its luscious surface quality, durability, and environmental friendliness on pieces ranging from turnings to band saw boxes and furniture. It works equally well as a solid, single color, as a thin transparent wash, or layered with other colors to accentuate textured surfaces.
I have been using and teaching about milk paint for several years and find a lot of people still have questions about how to take advantage of this wonderful finish. This article lays out my approach to using milk paint from mixing (it comes as a powder) to applying, and finally to finishing. I encourage you to explore this vibrant coating on your next project; your only limitation is your imagination.
What is milk paint?
Milk paint is comprised of fine powdered clay, pigment, lime, and casein, the protein found in the source of the paint’s name, milk. It is sold as a dry powder that you mix with water to reach a brushable or sprayable consistency. The added water acts as a catalyst to activate the chemical reaction between the casein and lime, resulting in a sticky adhesive substance that serves as the paint’s binder. Traditionally, the colors came from earth pigments which made for a softened, somewhat hushed color palette. Today, however, most manufacturers employ synthetic colorants to create a vivid spectrum of colors to choose from. At first, milk paint dries hard and chalky, but it is easily sanded and burnished to a silky sheen. Milk paint is also VOC (volatile organic compound)-free so it doesn’t emit toxins as it dries and can be disposed of easily by simply washing it down the drain or tossing it out.
Safety First
Milk paint is non-toxic, but while you are working with the powder, it’s important to take some precautions. Wear a good-fitting dust mask while mixing and sanding to avoid inhaling any of the fine powder. And wear safety glasses and gloves to protect your eyes and skin from the lime.
Mixing milk paint
Milk paint is mixed 1:1 with water by volume. In two separate cups, measure out equal amounts of dry paint and warm water. I prefer to use distilled water because varying pH-levels in tap water can cause milk paint to congeal in some instances. Add small amounts of the measured water to the dry paint and stir carefully to reduce kicking up the fine dust particles. Continue to mix the moistened paint until a smooth paste has developed. Incrementally add more of the water to the paste until it has all been incorporated. Let the freshly mixed paint sit for 10-15 minutes to allow all of the fine particles to “bloom” or become fully hydrated; a layer of fine bubbles will likely form on the surface of the paint, indicating the chemical reaction is taking place between the casein and lime. Prior to using the mixed paint, it should be strained to remove any small particles that did not fully incorporate. If your strainer is reusable, be sure to rinse it out immediately: dried milk paint will not redissolve. The finished consistency of the paint after blooming and straining should be like heavy cream. Add more water at this point to thin, if needed. Once mixed, milk paint has a short shelf life. Make only the amount that you plan to use that day, although I have had some luck refrigerating for short periods of time.
Filter out the grit. After allowing the mixed paint to bloom, strain it into a clean cup to remove any clumps. At this stage, it should have the consistency of heavy cream. Strain any leftover paint into an airtight container and store in the fridge for up to 24 hours.
Applying milk paint
Milk paint can be brushed or sprayed on nearly any surface (although the nuances of spraying are outside the scope of this article). I alternate between using foam and bristle brushes. I like wide foam brushes for broad and flat surfaces but prefer soft, natural bristle brushes for textured surfaces and for getting into corners. Generally, I find synthetic bristles are too stiff and don’t carry as much paint.
Milk paint acts as its own primer so it is not necessary to prime the surface prior to painting. In fact, milk paint prefers a natural un-primed surface that is sanded to about 120-180 grit so that there’s enough “tooth” for the paint to adhere to. If painting on pre-sealed surfaces, tight-grained woods, such as maple or birch, or non-porous surfaces such as metal, add Extra-Bond (see p.60) to the first coat of paint.
If painting a flat wooden form, apply the paint with the grain direction. If painting on the lathe, it’s important to use a very slow speed to prevent the paint from spraying everywhere. In all cases, it’s better to apply a few thin coats instead of a single thick coat of paint, which can easily drip, sag or catch debris from the air as it’s drying. I generally use three or four thin coats of milk paint on my work, but I have used up to seven or eight on textured items.
The Importance of Making Samples
I strongly encourage making paint sample boards to test different colors and techniques before committing them to a finished piece. Milk paint is quite durable, which can be both good and bad. It’s good for overall longevity, but it can be difficult to remove from surfaces, especially those with texture, should you make a mistake. I like to make several sample boards when I’m working on a project to inform my final decision-making process. Additionally, these samples are invaluable references to have on hand when working on other projects. I record the paint colors used, order of paint layers and sequence of processes on the backside of each sample board before I store them away. At this point, I have a library of sample boards that utilize a variety of color combinations, carving, texturing, and finishes.
Shortening the dry time. A warm (not hot) hairdryer can speed up the drying process, but be careful not to overheat the surface or the paint may crack.
Carving, texturing, and layering
Milk paint is very versatile; it can take on a variety of appearances and it works exceptionally well over textured surfaces to accentuate variations. Typically, I paint on top of carved/textured surfaces instead of carving through a painted surface. Carving into milk paint will dull tools quickly. I like to use carving gouges, rasps, planes, and spokeshaves to shape surfaces that either highlight the form’s contours or that suggest other materials, such as grass. When I am painting over carved surfaces, I like to use layers of contrasting paint. I have found that, after sanding and burnishing, the color contrast amplifies the visual impact of the textured surfaces.
Other effects such as crackling can be achieved through the application of specialized coatings and/or heat. See the Buyers Guide on page 60. And check out online Extras for more crackling techniques.
Sand through the layers. Generally, the last color applied (blue, in this case) is the color that will settle into the deepest carved section. The underlying color (yellow), or colors, will be revealed through sanding and burnishing.
Paint, crackle, pop. Using a product such as Old Fashioned Milk Paint Company’s Antique Crackle between layers of paint, you can achieve a variety of striking surface patterns. Or float a thick layer of milk paint across a surface and rapid-dry with a heat gun for a subtler effect.
Sanding and finishing
On its own, milk paint dries to a flat, lackluster, chalky finish. However, it easily burnishes to a smooth, buttery surface with a subtle sheen that is both beautiful and tactilely inviting. To create an aged effect, or to highlight a textured surface, build up layers of different colors before sanding some of them away with 220 grit sandpaper. Once you have finished sanding, burnish by rubbing the surface with fine steel wool, wood shavings, or synthetic abrasive pads.
Finally, although milk paint is durable and hard, it is not watertight and it will water spot and absorb oils and other dirt. So a protective top coat will help to keep your paint looking fresh for years. Most clear finishes, such as penetrating oils, wipe-on polyurethane, and wax will work over milk paint, but be sure to test a sample first. In all cases, the finish will deepen the color slightly. Make the decision as to what topcoat to use based on the intended purpose/function of the object you’ve made.
About the Author
Kimberly Winkle is a Professor of Art and the Director of the School of Art, Craft & Design at Tennessee Technological University. Working with wood and paint, Winkle creates furniture and objects with a careful balance of form, color and surface pattern. This is her first article with Woodcraft Magazine.
