Popping the Grain on Figured Redwood Veneer
Advice on a finishing schedule that will bring out the striking grain effects on some beautiful curly redwood. July 3, 2008
Question
I'm trying to pop the grain on some panels of curly redwood . I've achieved good results on part of the batch of panels (16), but am having a hard time getting acceptable results on the rest (23). I'm using gloss Mohawk WW nitrocellulose over Minwax wood finish, natural. The Minwax was used to highlight the grain without altering the color of the wood.
As stated, some of the panels have turned out with the expected clarity and uniform color, but others have come out with subdued grain and uneven light transmission/reflection. I don't think the finish is blushing, since it doesn't look milky and retarder has no effect. I've sprayed these panels with new HVLP equipment at both high and low temps, with the same results. Sanding was consistent with all of the panels. Does anyone know of a way to quickly strip the current coating from the panels without sanding? Does anyone have any opinions or alternative methods of popping the grain without a noticeable stain?
Forum Responses
(Finishing Forum)
From contributor C:
I've only worked with redwood burl. To pop the grain, so to say I used Potassium dichromate. It gave it a three dimensional appearance and made it look deeper by darkening the burls and somewhat lightening the surround wood. PD is toxic so use all safety precautions if you decide to go that route but I doubt if you will. You'll have to strip the coated panels and treat them all equally if you do. All that is needed to remove lacquer is lacquer thinner. The only hard parts would be if these are raised panels total removal from the corners and profiles if they exist.
You will need fresh clean rags and several times applying the thinner to make sure all is removed. It wont hurt to use 4/0000 steel wool either to help with the removal. Once the surface is chemically clean only a fine sand will be necessary to ready for the chemical stain. It is extremely important that you make samples on all the various wood scraps of varying grain anomalies that are in the panels to know for sure that it will give as good of results as I achieved on the burl. I would start out with 1 oz. per gallon and add more from there if necessary.
From the original questioner:
The panels are flat so no joints or features to deal with. I'll definitely be doing more figured veneer finishing on this project, so I'll check out the PD method, with safety gear, of course. The finish seems to be working during the spraying session, but deteriorates as the lacquer dries. Cure time on the sealer/stain was several days this time around. Maybe that's too long? Looks like I'm in for some lengthy experimentation to wring this out. Has anyone out there had any problems with spraying lacquer over
Minwax Wood Finish stains?
From contributor P:
Yes
Minwax can give problems. It doesn't always, but any MLC distributor can formulate the
Minwax color in a Woodsong II stain which can be coated in 20 minutes if you really have to. An hour or two is better. They could easily give you something that approximates to "natural". If you are using NC lacquer topcoat, have you considered shellac to pop the grain?
From contributor C:
You can use shellac 1 lb cut to seal in first then machine sand off and apply again. This will pop or define the grain better or you can also use very weak dye. Use a water soluble solution to the wood and again sand it off the non figured areas thus leaving it in the figure. If done more than once each time will continue to add more visual difference between the two. This is a method I use for highly figured woods such as curly, quilted, burl and others on musical instruments when I want a stunning affect.
From the original questioner:
Thanks for the new tips, guys. I'll definitely give the shellac a shot on my next figured wood finishing challenge. I did run test panels on the redwood before committing to this finish, eliminating several sealers and topcoats. I just can't seem to get a handle on the problem with it. This veneer is very striking and I know it has great potential to glow and shimmer, but the topcoat looks more translucent than transparent.
Could rapid flashoff cause the topcoat not to bond as thoroughly to the sealer? The lacquer seems to be drying in minutes. Is this normal? Once I had decided that blush was not the problem, I didn't use retarder on the last run. I'll have to spray some test panels using retarder. Also, is a random orbit sander acceptable for this process? I was advised by one colleague to use a jitterbug, but I don't have one. At this point, if it would solve this problem, I'd buy three of them. Once again, thanks for the input, and any other advice would be greatly appreciated.
From contributor S:
I agree with not using a
Minwax product under your lacquer. Could your problem be the lacquer itself? You refer to this as Water White even though its gloss does it look milky in the container. When building a full finish with W.W. lacquers they tend to become plastic looking and lack clarity.
From the original questioner:
The lacquer is quite clear in the can. Trying to sand just the springwood or summerwood in this case would be a labor intensive nightmare, wouldn't it? The grain (wavy) pattern in this veneer is not as tight as it usually is in curly maple, but there is quite a bit of character.
The staining process you describe sounds like the way to go, and I wish I had known about it before I committed to what I'm doing. I'm assuming you mean the potassium dichromate process. I don't have a lot of experience with figured woods. Live and learn. This is becoming an expensive lesson.
From the original questioner:
Yeah, it looks like a wetting problem to me. I'd like to try to slow the cure time on the nitro as much as possible, without compromising finish durability. I will try a test with no sealer and see how compatible it is with the panels that are looking ok. How much retarder can I include per quart of lacquer?
From the original questioner:
I also have some larger panels of waterfall sapeli (proprietary moniker, probably) that I have to finish. The client actually prefers a flatter overall appearance for all woodwork, but I thought this particular application would be more striking with the film finish of a lacquer. Can I achieve good grain highlighted results with an oil finish, such as tung with hand or machine-buffed wax, or maybe one of the Maloof finishes.
The redwood panels are going on the ceiling, but the sapeli panels will be much more accessible, on foyer walls. There will be considerable construction activity in the area after installation, so any bumps or scrapes will have to be reparable. The surface areas these panels are covering are large, so another misstep like the one with the redwood will necessitate a suicide reaction. Thanks again for all contributed advice.
