Why did my two coloring jobs come out different?
I just finished two bedside tables in q-sawn white oak, built from the same stock wood pieces. I mixed up powdered dyes according to the directions using de-ionized water (the packages say they are aniline dyes, but I think that is a throw-back term). I experimented with at least 10 different combinations and tested them on scrap pieces sanded to 180-grit, the same as the tables. I chose a 14:1 ratio of dark golden oak and brilliant crimson. The dark golden oak by itself resulted in a cool, greenish color and I added the crimson to warm it up. I used graduated hypodermic syringes to control exact color ratios.
The first table came out perfect with a warm tint without too much red, just enough to kill the green. I set it aside and completed the second table within three days of the first. I used the same dye I had already mixed, from the same jar, again applied with a brush and almost immediately wiped down, but the second table came out noticeably cooler, with the green dominating the red. I tried a second coat, but that just made the table darker without warming it up. I made sure the dye solution was well mixed. I decided to add a little more red, being careful to not get carried away because I didn’t want my work piece to look like a Santa Claus suit. I did this two more times until the golden oak:crimson ratio was 4:1. I stopped at that point because the second table was getting too dark. In the end, the table remained greenish, never warmed up and now I have two bedside tables that are noticeably different colors.
Questions:
1) Did the three days the dye sat in the jar cause this discrepancy in color? The printed instructions say that these stain colors will deteriorate over a long period of time, but this was a very short period.
2) I have been taught that red dyes are “fugitive”, but I really don’t know what that means (I should have asked my tutor). Does that sould like it could have affected this color mixture?
3) I never re-heated the dye, but I did not see any re-crystallized powder or any precipitate at all. Should I have re-heated it for the second table?
Replies
Differences in wood?
I am in agreement with Steve regarding the dye and your procedure. According to that, there shouldn't be a problem. That leaves only the wood to cause a difference. You said the wood for both tables came from the same stock. Does that mean the same board, the same tree, ... ? I would suggest you take samples of wood that you know came from both tables and apply the same dye at the same time. See if there's a difference. If so, then its the wood.
I had a professional finisher tell me years ago to always apply coloring to freshly sanded surfaces. Wood surfaces change with time. Even the Forest Product Lab Woo Handbook says that adhesives become less strong if applied to surfaces the have not been freshly milled.
I can't tell you what went wrong. I'd have to be there to do that. I can tell you how to fix it. Clean off your dye with water and chlorine bleach. Sand just a little too. Now start with a clean slate and some scrap that matches the table top and rework your dye tint till you get a good match. Do it by eye, it is unimportant that your procedure match, it is ESSENTIAL that your finished look matches. As a professional with lots of experience making critical matches I have learned NOT to fall into the trap that you did. The look is everything the procedure is mostly meaningless. Focus your efforts where it counts!
I can understand how one with loads of finishing experience can, by looking, judge when enough dye has been applied. But given that the finished look will be vastly different after the top-coat, how does a novice know when the proper amount of dye has been applied? Common wisdom is to do sample boards then replicate that procedure on the actual project. This would necessitate focus on ones procedure, and to ignore what their eye tells them. Only after many finishing jobs is one able to finally "know" when enough is enough.
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