Here's the situation:
You've got a wall currently painted with latex-based paint (or primer), and you want to...
- Create a more traditional looking decorative finish, OR
- Cover the paint with a "green" alternative.
In general natural finishes require porous surfaces to adhere to. However, latex paint or primer does not provide an ideal surface for these finishes to adhere because latex is inherently non-porous. In addition, there may be chemical incompatibilities between the existing and new coatings such as when using lime.
One must consider what is realistic when envisioning the desired outcome. Factors include cost, how many coats will be required, whether to purchase or make your own finish, and what preparation, if any, the surface will require.
There are several options for coating over existing latex paint, some of them natural and some not natural (but still considered nontoxic or "green.") The first step in choosing a new coating is to assess the existing surface to be covered.
Assessing the Painted Surface
To begin it is important to know what the existing surface is. In most houses this usually means latex paint or primer.
In some older homes, wall coverings can be more difficult to determine.
If the paint is historically correct or painted before the advent of latex paint in the 1950's, it probably has an oil base. Oil paint and other glossy paints are the most difficult to cover and will require the most surface prep. Unless you plan on covering the old oil paint with new oil paint, this coating must be given some tooth and partially removed in order for anything else to adhere. BUT A WORD OF CAUTION: Many old oil paints both for wood and walls contain lead. This is extremely toxic and must be removed by professional means to protect from lead contamination. Makes you not feel as bad about latex, doesn't it?
Some older plasters may appear to have paint on them, but if it has a flat, velvety finish it is more likely harmless distemper paint made from animal glue. This type of paint must be removed before a new finish can be applied, but it is washed off the wall with water and good scrubbing.
In this article we will be focusing on re-coating the most common type of paint encountered in today's homes - latex. Primers and matte/semi-gloss latex paints usually provide the easiest painted surface to tackle.
As with any surface to be recoated, it must be free from dust, dirt, grease and any flaking or peeling paint. Without modern additives, natural paints and finishes have the BEST chance to adhere if the wall is lightly sanded and washed with a tri-sodium phosphate solution and thoroughly rinsed.
In some cases, a modern water-based acrylic polymer additive must be employed when covering existing paint. These can be VOC free, non-allergenic and inert if you choose the right product. Acrylic is not the same as latex and those suffering from latex allergies often choose acrylic based products as an alternative.
An important consideration when choosing a natural or traditional finish is whether you need it to be opaque (to completely hide an existing color), or you want a more translucent formula to get an effect "over the paint", (rather than trying to conceal it).
A wall with dark paint you wish to cover with a lighter, opaque paint will require more coats than a white wall that you just want to give a wash or color effect to.
Consider what is important to you in choosing a new wall coating and what reasons you have for not proceeding to the hardware store's paint chip aisle to buy a gallon of premixed latex color.
These usually include:
Exploring the Options: Opaque Paints and Primers
These coatings are recommended in situations where you wish an existing color to be covered or when you wish to create a white or light colored base for other finishes.
Our recipe for Swedish Paint can be used as an interior paint, and has excellent adhesion, especially if the oil is added into the recipe. We prefer this flour paint recipe to others we have found because of its natural anti-mold formula. This is a good choice for those wishing to make their own paint using commonly found ingredients, however the cost depends upon which pigment is chosen to color it.
Oil paint is usually considered just for wood. However it can also be used as wall paint, and was the primary interior paint before the advent of latex in the 1950's. It creates a durable, washable, gloss coating with intense color. Pigments absorb in oil differently so it can take some experimentation to determine the pigment to oil ratio. One idiosyncrasy of oil paint is that it yellows over time. This patina can be considered a pro or a con depending upon which color you choose.
Exploring the Options: Translucent Finishes to Transform
These finishes are recommended over white paint or primer, or over an existing paint color you wish to enhance. Because of their translucent or transparent nature when dry, they create a wonderful forum for the beauty of our Ochers and pigments to be realized. These finishes can be manipulated by using different applicator tools to change the effect.
In the past, lime washes on top of previous paint were not possible. However with our superior [Lime Prep primer], (zero VOC) you can cover latex paint and achieve this traditional look as long as subsequent coats of lime wash contain an additional binder to assist with adhesion. Among these could be oil (may yellow over time), casein or PVA.
Lime Wash is a multiple coat application in which subsequent coats can be manipulated for darker effects. It is also the perfect base for wax finishes to protect, add depth of color and create effects from dead flat to gloss.
These paints can be either homemade or purchased as a readymade product. Milk paint can be used on walls, however it has two characteristics that must be taken into consideration. First, this traditional coating needs an absorbent surface in order to adhere. Secondly, it takes several coats to achieve a completely opaque coating. In one or two coats, it does impart a beautiful Old World finish of a pigment wash, and can be manipulated to create varying effects. Milk paint can be further decorated and protected by using any of our waxes as a topcoat.
Although we do not recommend homemade milk paint for application over existing paint, in some circumstances this simple glaze that uses casein (milk) as its base can adhere properly because of its added oil. However, it is recommended that it be tested for suitability.
Here is an easy, inexpensive finish that can mimic the beautiful matte appearance of traditional Distemper paints used over plasters. It is a velvety finish that, when coated with our Clear Seal Satin, becomes washable.
Waxes: The final touch or an easy enhancement
The use of waxes for finishing on walls is an ancient technique that remains unknown to many. It is amazingly simple and has both decorative and practical applications.
On the practical side, waxes can coat an unwashable finish making it washable, and can be used as a final finish to protect. On the decorative side, waxes can be tinted with micas or any Ocher or pigment to easily enhance a paint color or give a decorative effect.
Used tinted or untinted, waxes can give a shine to an otherwise flat wall. Add mica powder and it gives a sheen that changes with the light as you move around the room. Boring white walls can be transformed into swirls of delicate color. Colored walls can be given added depth by adding a complimentary color on top.
Waxes can be divided into two categories: traditional solvent based such as our Roman Beeswax Polish, and water-based waxes such as saponified beeswax. Waxes can also be created at home from recipes. Since a little bit goes a long way, using wax to decorate is practical and a cost effective technique.
Solvent waxes are not as washable as their modern alternatives and must be removed in the future if the wall is to be painted. Solvent-based waxes also have a strong odor during application and for a short time thereafter as the solvent evaporates.
As with any coating, waxes should be tested when used over existing finishes to be sure they will perform as expected and give the look you desire. Which wax you choose depends upon your personal preferences and the desired effect.
The formula for adding Ochers, pigments or micas to a wax is the same for any type of wax. The maximum ratio is 1 part Ocher, pigment or mica to 3 parts wax. The less used, the softer the effect. To read more about our waxes and the special effects you can achieve, visit our Finishes and Waxes page.
It is possible to coat existing latex paint with alternative products as long as certain requirements are taken into consideration. In addition to the products and recipes discussed here, there are many new products coming onto the market that offer alternatives to common latex paint. Each has advantages and drawbacks, and mMany will work with our Ochers, pigments and micas.
The rule for proceeding once you have chosen any alternative finish is to TEST. Test your formula in a large enough area (at least 1 sq foot) so that you can see what the coating looks like in the light of that room. After your test patch is fully dry, test for adhesion. Once dry, your paint should not powder off when rubbed or flake off the surface. Wet a sponge with a Teflon scrubbing side and rub the finish with moderate pressure to see how it holds up. Not all paints and coatings will hold up to this type of scrubbing, but they should not come off with ease.
Disclaimer: The author of this article assumes no responsibility for the appropriateness of a finish to any individual circumstance. It is up to the end user to test and determine compatibility, appropriateness, and durability of a finish for their particular use.