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Stains—Part 1

8/15/2014 4:00:00 PM
Article by Bob Bein

Hello again and welcome back. Today, I find myself once again addressing a subject that needs much more space than I am allotted: Wood stain. Staining wood to enhance its color and highlight its beauty is something that has been done for millennia. When done correctly, it adds depth and character to a piece of furniture. When done incorrectly, it makes wood look blotchy, cold, and lifeless. Because this is such a large and detailed subject, I will attempt to make sense of staining wood in two parts.

First, I would like to talk about what typically starts the staining process, a color sample that has to be matched. Many of you produce furniture or woodwork under contract for a customer that wants you to match something that already exists. Typically a color sample is given to you in the form of a small panel, but it might also be a piece of furniture or wood part of some kind. Before attempting to match the color, the first thing to be assessed is the clarity or brilliance. Typically, stained wood falls into one of three categories: Transparent/brilliant, semi-transparent or muddy. Sometimes, in the most difficult circumstances, you can have two of the three happening at the same time. We will talk about all three, and the approach to matching them, as well as matching the color.

Let’s start with transparent samples. When you pick up a sample with exotic veneer, hold it to the light and tilt the sample back and forth several times. If the character of the veneer changes from dark to light and back to dark, it is a good sign that the stain is transparent. We often refer to this as “Flip”. Also, when the wood appears to be a color that is not what you know the wood color to be but doesn’t look like it is stained, it has high transparency. Typically, tight grained, exotic woods like cherry, birds eye maple, anigre, and lacewood will be very transparent when stained and finished.

The next class of stains is semi-transparent stains. These samples typically are showing good clarity of the grain with some flip but not as much as the most transparent samples. It is easy to see that a stain was applied in some fashion. In some cases the flip does not appear at all. In ring porous woods like Oak or Ash, the deep pores are darker, indicating that a stain has been applied.

The last class of stains is what I refer to as “muddy” or semi-opaque stains. These are the easiest to see. Typically the character of the grain is not coming through the topcoat. The grain will look flat and lifeless with little character. Sometimes there is a combination of the effects. Finishers with a sharp eye can sometimes see that a sample has a transparent, brilliant base with a second layer of stain applied over the top of the first. Duplicating the sample using the same process can be very difficult. Even the most experienced finishers with a trained eye can spend several hours, or even days, developing a system that will match the sample.

No discussion of stains would be complete without a brief discussion of the types of products that will stain wood. Most, if not all of you are aware of the difference between pigments and dyes. Dyes are created from a chemical process joining chemical elements together along with metals like cobalt to create colors that penetrate deeply into the pores of the wood to stain the wood while maintaining good transparency and brilliance. Pigments are finely ground particles of inert materials like oxidized iron and other minerals that are suspended in solution. Depending on the size of the particles, they will impart a semi-transparent or muddy look to the wood. How transparent or muddy depends on how fine the particles have been ground. Products can be added to increase the opacity or muddiness of a stain, but rarely can a pigmented stain be made to have more transparency.

So, let’s break down the different categories of woods so we can discuss the approach to staining them. Wood is placed in two basic categories: coniferous wood and deciduous wood. Conifers are trees that have slim, needle like leaves that stay green and attached to the tree year round. They are typically referred to as evergreens. Examples of evergreens are pine, fir, spruce, and larch. They typically have high levels of resin. Deciduous, or broad leaf trees, are trees that typically have wider leaves that turn color in the fall and fall off the tree. Deciduous trees can be further broken down into two categories: Ring porous and ring diffuse. Ring porous trees have a very distinct difference between the part that grows fast in the spring and the part that grows slow in the late summer and fall. The fast growing spring wood has very deep pores. Typical examples are oak, ash, hickory, and chestnut. Ring diffuse woods have very little variation in the speed of their growth from spring to fall, therefore there is very little contrast in the grain of the wood. Typical examples of ring diffuse woods are maple, cherry, birch, and beech. There are exceptions to the rule of how you approach staining of these types of wood as well. Cypress is a deciduous tree that responds more like a conifer. European larch is a conifer that responds more like a deciduous species. That’s all I have room for right now. Next month I will continue the discussion by explaining the different approaches used to stain these different types of woods. Until then, keep finishing.

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