Can these techniques apply to other mediums and how do you paint wood to look like wood?

Questions:

I always thought that lighter colours would be more transparent and darker colours opaque, but have trouble understanding why the opposite is true. Does this rule only apply in the Flemish Technique. Could you expand on your answer to someone's else's question, the limitations of the Flemish technique, please. Thank you

Answers
OK, I'll try to answer both, well, all three if you include the headline question.

White covers well, and most of your lighter colors will include white, which is opaque. The dark colors, even when used straight from the tube, will allow some of the underlying color, line, or whatever, to show through the layer of paint. I'm not a chemist, so I can't break it down any further as to the why's this is so. You must see it to believe it. Of the three common blends of white oil paint, Zinc and Flake are a bit transparent too. Titanium white has the most covering power, thus the most opaque.

This applies to mostly oils as other mediums, acrylics, watercolors, have different properties that I'm also not familiar with.

As far as limitations, I don't think there are any. When you look at paintings done in this technique, (especially realist works)I have never seen any thing better. Not to say acrylics and water colors cannot achieve a fantastic painting. They can in the hands of a Master. But when you hold up the acrylic, or the watercolor, against a painting completed in oils, the oils (in my opinion) have a better range in value, deeper and richer colors, brighter and more glowing effect, and as far as longevity, nothing has proven better, (except charcoal and graphite, which we have found in caves over thousands of years old).

As far as how to paint wood. I'll have to include that in a demonstration, but suffice to say that starting with a base tone, and your grain depicted using a darker tone and applied after the base dries is the normal approach. There are some interesting brush techniques too, that are used to achieve it. I find that using a fan brush loaded with a fairly thin mixture of the darker tone, then twirling the brush as it is stroked will get a good effect. I'll include an example if I can find one and a close up. Hopefully it will help you!