Ok.. so blotch. Wood blotches… its part of woodworking. Some woods blotch more than others… some don’t blotch at all.
Blotch has come up a few times recently in my life. It was also briefly talked about on a recent Woodtalk podcast, where they offered some good info. But I thought I would write about it too. This will allow me to go into greater detail than it would had I typed something in forums and website comment sections.
Frist off… as I state often in these types of blogs.. this is MY opinion and I have NONE, ZIP, NADDA, NIL scientific evidence to support my claims except my personal experiences. Again… I am using my findings from personal experiences. I strongly suggest you try things out for yourself and draw your own conclusions.
Now that I am off the hook when you mess up your project… lets get down to business.
What is blotch?
As far as I can tell, and what experience has taught me, blotch is just grain variation in the board that when a finish is applied will absorb finish differently (more or less) than the rest of the board.. In some cases and in some peoples opinion, it can be called ‘unsightly’. I like to think that if the blotch was smaller and there were more of them, it would be considered figure.
If you, like many people don’t like the look of blotch, there are several ways to try and control it. There are several products on the market that can be used. I personally have only ever used Minwax pre-conditioner. I applied it on some pine before applying an oil based stain. It worked ok. But… I have not used oil based stains since I discovered water based aniline dyes. So.. needless to say, my experiences with trying to control blotch with a dedicated product is fairly small.
I suggest that you read either/or/both Jeff Jewitt’s and Bob Flexner books. They have way more information and can help significantly in the science area of things.
Aniline dye and Blotch!
Again to reiterate… these are based off my personal experiences. I used to work exclusively in pine (because other woods were too expensive and I was not very confident in my skills) and I used to use lots of oil based stains. Pine blotches. LOTS! Enter the pre-conditioner. ICK!
Then, one day, many years ago, I decided that I wanted to up my game and contacted my favorite woodworker that is in the lime light. Glen Huey. We emailed back and forth many times and he introduced me to aniline dyes. My first experience with the dye was on a pine chest that I had made. I did not know how the dye was going to react and how badly it was going to blotch, but I put my worries aside and applied the dye as per instructions. No blotch! I made several projects with pine and finished with dyes… I have had NO ISSUES with blotch.
ALL of the pine finished with pre-conditioner and oil based has minor blotch. NONE of the pine with aniline dye has ‘unsightly’ blotch. There are minor colour variations due to changes in grain.. but it is NO WHERE close to the oil. For example. On a scale of 1-10 , unconditioned pine can vary from 6-10 (oil based). The preconditioned stuff is some where in the 3 range (oil based), and the aniline dye (water) stuff is maybe a 1.
Maybe this is because the dye is deeply penetrating the wood and dying all the fibers, where a stain has little penetration and is absorbing inconsistently thus magnifying the appearance of the blotch??? Speculation….
I would also defiantly say that the aniline dyes give a deeper and more consistent colour.
Blotch on hardwoods
I have also had experiences with blotch on hardwoods. Mostly cherry. But these experiences are a little different than with pine. Mainly because I have never tried to dye or stain cherry. I am of the mind that I try to pick a wood that is the colour I want the finished product to be, so I don’t have to deal with these colouring issues. None the less, cherry will blotch no matter what you put on it. In my case, its mostly BLO and shellac. I know there are ways to control this (based on magazine articles and such) but I have never bothered to try any of them. Why? Because I like the way it looks. The wood looks more natural to me. Even in the magazines, they show how they controlled the blotch, and the blotch controlled wood does not look as deep and rich to me. Besides, because cherry darkens with time, the blotch fades.
Maple is a different story all together. I don’t really like the look of regular maple, and I don’t use it very often unless its highly figured or spalted. And like I mentioned before, I think of blotch as large figure. So figured maple is nothing more than really blotchy wood. Using aniline dyes can really enhance the highly figured woods. But if a plane maple board has some minor splotch on it.. I honestly have no idea what it would look like. Maybe think of it as radio waves. The higher the frequency, the more figure and the lower the frequency the less figure. But the low frequency is still going to have some spots where it goes up and down, but might not be as visually apparent once dyed?
In the end, I think if you have any worries about blotch, your best option is to seal the wood with shellac or use a pre-conditioner. But do test pieces first.
Maybe I have put way too much thought into this…...