It’s all about the color! Stains and finishes 101

It’s all about the color! Stains and finishes 101

 

This blog post is very information heavy.  Most people only want to know what color their furniture will be stained or painted, and don’t care about the particulars of finishing.  Some customers however, do want to know if the finishes are safe and how they are to be cared for.  I tried to provide as much information about stains and finishes as I feel would be necessary for the average person to be able to make an educated decision.  I also provided some info at the end from the EPA on some of the safety issues for those who are interested.  Maybe we can deal with stain colors in a future post; this one will be long enough as it is!

First we will focus on the two types of stains that dominate most furniture finishing today.

Pigments: A pigment is a very finely ground, solid-colored particle. Pigment stains are usually suspended in a binding agent to help attach the pigments to the wood. They are usually “heavier” than the binder used and settle to the bottom of the can. Pigments actually color the wood by getting into the pores on the surface and don’t penetrate deeply into dense woods. Pigment stains will sometimes mask the more wild grain of some hardwoods.

Dyes: Dyes are very small molecules and very translucent when compared to pigments.  Tree Bark, coffee, tea and food coloring are examples of dye stain. Dye stains actually penetrate deeper into the wood fiber since they are smaller. This is especially helpful when staining hardwoods where the grain is very dense. They usually enhance and accentuate the natural character and contrasting grains of the wood.

Neither a dye stain nor a pigment stain is superior to the other.  The degree to which they stain each appropriate wood is mostly dependent on the length of time they are left on the wood and the softness or hardness of the wood. Soft woods like pine and cedar have large open pores, where hickory and hard maple have small dense pores. The larger the pores in the wood the deeper the penetration of the stain and the richer the color can become. The openness of the grain can also be affected by sanding, bleaching, washing, stripping or sealing the wood before staining.  Many professional finishes, and most commercial stains, mix both dye and pigment elements together to enhance the beauty of real wood furniture. This is an excellent way to color woods such as brown maple, hickory, or cherry because it will balance out different variations in the woods natural color and grain patterns.

Paints:  Paints are heavy pigments of color suspended in either water-based or oil based solvents.  Paint will completely cover over most fine grain patterns in wood.  Rough grained wood like oak, will still display the coarse pattern through at least the first 2 to 3 layers of paint.  Paint bonds only to the surface of wood and does not usually expand and contract with the breathing of the fibers as the wood ages and dries.  This leads to cracking, chipping and wrinkling of the paint over time.  Painted surfaces will show imperfections in the wood more easily than stains.  Some softwood like pine and cedar can “bleed” sap through the paint over time.  Brown maple and poplar are often the better choice for painted furniture, due to their finer grain and lower cost than other hardwoods.

Once your furniture has been stained or painted, there should be some type of top coating or “finishing” applied to seal and protect the wood. Most professionals will apply a sanding sealer to the stained surface first.  Staining tends to raise the grain of the wood, so a sealer will first close off the pores to seal out moisture.  This sealer is then sanded to smooth out the rough surface of the raised grain and prepare the surface to receive the top coat.  Top coats are available in several different sheens.  The sheen is how glossy the finish appears on a scale from 0 (flat) to 100 (high Gloss).  We use 20 sheen as our standard top coat.

There are two main types of top coating or final finishes; penetrating and film. 

Penetrating finishes such as linseed oil or Tung oil penetrate deep into the wood to seal the wood from moisture, but it requires many coats over a long period of time and is very labor intensive. The drawbacks are that they don’t protect the wood itself from scratching and bumping, or against other household chemical products, and they dry from the outside in so they need to be re-applied regularly to keep the wood protected from moisture. But they also don’t contain the harmful chemicals some lacquers and poly-urethanes do, so they are more environmentally friendly.

Film finishes such as varnish, lacquer and urethane are built up using layers of the finish to completely seal and protect the wood from moisture.  Older versions of this type of finish were unreliable over time, often scraping off easily with a fingernail.  The newer versions, such as conversion varnish, use a catalyst agent to harden the finish and create a long lasting resistant coating. This is much like epoxy glue where you mix a catalyst with the glue and when hardened, it makes a much more powerful bond. Conversion varnish is fast drying, non-yellowing, and cures from the “bottom up” so the solvent must work its way out of the film so the finish molecules can cross-link. Once cured, usually in 2-3 days, this product provides superior protection from water as well as most common household chemicals. The drawbacks to some of these finishes are that they contain organic chemicals in order to aid in the curing process.  VOC’s or volatile organic compounds are regulated by the EPA to keep them under “safe levels” (see section I below).  These compounds are emitted as gases as the finish cures and are greatly reduced in 2-3 days.  Our conversion varnish is a low-VOC qualified product that is certified non-toxic once cured.  It is used on everything from our tables to our cribs to provide a strong, water and chemical resistant finish for your furniture.

Caring for furniture finished with a conversion varnish is very easy.  You can simply wipe it down with a damp cloth and you are done. No polish, wax, pledge, or other product is needed to keep it looking good.  If something does stain the finish such as a permanent marker or newsprint, you can even use fingernail polish remover on a rag to clean it off.  While not scratch proof, it is resistant to normal wear.  This finish is also resistant to heat, so a warm plate from the microwave will not hurt it.

 

SECTION I   VOC’s – Volatile organic compounds are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.  (EPA)

Organic chemicals are widely used as ingredients in household products. Paints, varnishes, and wax all contain organic solvents, as do many cleaning, disinfecting, cosmetic, degreasing, and hobby products. Fuels are made up of organic chemicals. All of these products can release organic compounds while you are using them, and, to some degree, when they are stored.

The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

Source EPA

Chemical resistance tests:

Using the 0 to 10 system with 0= severe effect, 10= no effect

Item

Lacquer

Conversion Varnish

Hair Spray

0

10

Perfumes

0

10

Acetone (Nail Polish Remover)

0

10

Shoe Polish

3

7

Soda (Cola)

7

10

Ketchup

7

10

Coffee

5

10

Alcohol

5

10

Hot Water

5

10

 

 

 

 

 

 

 

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