Troubleshooting Pencil Dents in Polyurethane over Maple
Here's a long, involved thread about how to handle a problem with a soft, dentable finish applied over a beautiful one-of-a-kind custom Maple countertop. July 18, 2013
Question
Against my better judgment we recently used Minwax polyurethane for a countertop finish over hard maple. Four coats with a hand rubbed final coat. It actually looked better than I thought it would. Today, while re-visiting the job, the customer pointed out a small area that had indentations from a ball point pen.
It seems someone had written down some notes on a piece of paper and it transferred through. I decided to test the finish myself so I wrote a couple small letters on a scrap of paper in the same area. Even with very light pressure it left marks. The poly has been on over a week, enough to have cured I would think. I realize a ball point pen probably shouldn't be used on a wood counter, but I thought this finish would take a little more abuse than the light pressure I used. I hate to strip all this off.
Does anyone know of anything we could use over the poly for a harder finish? We used CV on all the cabinets but were worried it might be too brittle for a countertop. This isn't a counter near a sink, just a raised breakfast bar.
Forum Responses
(Finishing Forum)
From contributor R:
Unfortunately putting a harder finish over a softer one is asking for trouble. If it were me I'd look into professional finishes for the job. Minwax is strictly an amateur material. You have options with solvent-based products, such as bar lacquers and varnishes. You also have a plethora of waterborne finishes. None of these options will work well or reliably over a soft top coat. Mistakes are just opportunities for learning.
From contributor F:
There really is an easy and only solution. You have two options. One, remove the top and take it back to your shop and strip it and spray CV on it. The other option is to build a new top and spray that with CV and take it to the site and replace the one installed. Since you had the option from the beginning I do not know why you didn't use CV in the first place. Where did you get the idea that CV is brittle? It isn't. Sprayed poly (2K) is a different animal and I use that for restaurant tabletops, but I would not recommend you use that. That is not for beginners. Just redo it, no big deal you learned a lesson.
From the original questioner:
Thanks for the responses, I appreciate the input. Replacing the top is not really an option as this slab is really one-of-a-kind bookmatched piece that they really love. They are also open to a glass top cut and ground to fit the shape which might be another alternative.
I'm not exactly an amateur, just haven't worked with polyurethanes much over the years. I've been building custom cabinetry for close to 40 years, sprayed mostly lacquers in the early years, and in recent years CV but I have heard even on this forum that CV, while very hard, tends to be prone to cracking under stress or impact, and chose not to use it for that reason. Now I guess I've learned another lesson. I actually did a little test last night with a ball point pen on a piece of cherry finished with both Agualente and Endurovar. Both were harder than the poly finish which does surprise me. I'm wondering if the poly has failed to completely cure for some reason. Not that it matters much at this point.
From contributor Y:
Upon reading this I picked up a pine outgrowth piece I had finished about a year ago with Mudwax fast dry poly which my son had at his house when I was visiting. Now this sample is several months old but the wood is very soft. The piece has about ten coats of FDP and I could not get it to indent with normal or far past normal pressure up to about five times as hard as I would normally. So I'm curious as to whether this is what you used or not?
From contributor F:
As far as you hearing on this forum that CV is brittle that I have no doubt. There are some on here that spend more time reading PI sheets then they do actual finishing and then they pass along what they read as gospel. I work every day with the products of which I write and I have been doing so for over 30 years.
From the original questioner:
To contributor Y: Yes, that is what we used. Although it's not a product we normally would work with in our shop, I know it's commonly used by many floor finishers in our area including the pine and cherry floors in our own house where it's held up pretty good.
Contributor F - I have used CV both Sherwin Williams and Campbell for years and never had any problems either, but after hearing this on the forum I’m just unsure about its use for a working countertop as we don't do a lot of wood tops that see writing, etc. on them, mostly kitchen and bath cabinetwork. Now the customer is asking about a two part epoxy bartop finish floated over the existing. I'm looking into that although I don't personally care for the look.
From contributor A:
Any clear coating system on a wood counter in the kitchen has serious limitations that you need to prepare your customer for. A week or ten days is really not enough for a full cure on the varnish especially if you want to rub it out. Thirty days gives me a lot more confidence. If your coats were heavy or rushed it could extend the dry/cure cycle quite a bit. In general, a rubbed finish will show marks easily as compared with an out-of-the-can satin or semigloss sheen of the same product
Going over the poly with anything else is digging your hole deeper. At this point you need to know what the next step will produce and not just a hope and a guess. I would suggest doing a sample and duplicate what you did before, but instead of rubbing it, just apply a satin or semigloss final coat. Then give it the same ballpoint test after a week, two weeks, and one month. Like Contributor Y I would not expect to see this finish denting so easily.
From contributor G:
Polyurethane needs at least 30 days to cure completely. Ten days and the finish is still soft. Give it a long month and try the test again and it should be much better.
From contributor B:
As others have noted 30days is minimum for curing and rubbing them out will only highlight scratches. And really there is no "perfect" finish that will never show scratches. I've built tables for a national restaurant chain using 1.5"sq mahogany edging (left unfinished) left 1/4" proud then filled with a 1/4" of polyester resin. They were incredibly durable but they still got scratches which every few years they'd be brought back in to re-rub them out.
So I would recommend the following:
1. If it's non-food counter top consider a glass top I've done this on numerous desks.
2. Re-finish with a lower sheen, don't rub it out and tell them to stay off it and let it cure.
3. Depending on your level of pain/ability and their budget strip it and re-coat with epoxy to stabilize the wood and add hardness then top coat with a polyurethane.
From the original questioner:
Are you saying you can put poly on top of the epoxy finish? Is that just to get the "sheen" wanted?
From contributor G:
Just make sure that the epoxy will support a finish coat. I use the West System and if you want to finish it they have a special hardener for the application. #207 with their regular resin will allow a poly finish on top.
From contributor B:
To the original questioner: Yes you can put poly over it. Contributor G is on the money with the west system. That's what I've used.
From contributor J:
If you and your customer are ok with the glass top over the existing finish would be best to go that route in my opinion. I know you said this is over hard maple, and from your experience you mentioned are you sure the area in question is hard maple. The finish is doing what it’s supposed to do. Even with a conversion varnish if the wood is soft underneath the finish it will still have pen marks telegraph through. A finish will not really protect the wood from something like pen marks unless you went into using a 2K polyurethane or polyester type of finish, but depending on how thick that type of finish is still may or may not prevent the pen marks.
From the original questioner:
Yes, the wood is hard maple. I actually cut and milled the tree myself and have been doing so for many years. We harvest both hard and soft maple, cherry, ash, and butternut from our property and I've had about 40 years experience identifying trees in our area (NE) along with my woodworking experience. This piece is a large bookmatched counter made from two approximately 18" slabs containing some darker heartwood along with the more typical white. It’s a very pretty piece.
From contributor J:
That is awesome that you are able to cut and mill your own lumber from your own property. Also to have book matched a piece for the countertop, that is just a level of quality you don't see or hear much of anymore. Most people I've found don't appreciate quality and that level workmanship either.
From the original questioner:
Here's a shot of the top and a few of the cabinets. Cabinets are butternut with a few accent panels of spalted maple. All door panels and end panels are bookmatched.
Click here for higher quality, full size image
Click here for higher quality, full size image
From contributor J:
Thank you for posting the pictures. Very nice work, I like the fact that you kept the finish light and was able to show off the wood.
From contributor R:
I like the book matched door panels. In thinking over your counter problem, I think an epoxy on the bar is the way to go. One thing nice about using a West System like epoxy is that top coats are fairly straight forward over it. I've sprayed and rolled gel coat, bottom paint and varnish over it and it stood up to pretty harsh marine environments with the right surface prep. Good luck with this project.
From the original questioner:
I think the epoxy is the way to go. I'm planning on a sample on maple that has received poly first, just to make sure the customer likes the final look and then if all is ok, proceed.
From contributor A:
To the original questioner: I'm having difficulty understanding what your plan has evolved to. Are you still trying to find something to go over the
Minwax Poly that didn't cure? Are you removing the top back to your shop for this redo? Are you planning to strip or sand down the top on site? What are the steps you plan to do on the sample?
I understand the Marine epoxy used as a base for varnish topcoats is a great system for wooden boats, but seems way overkill for this situation, and difficulty compounded by the fact you have no experience with it. When I'm faced with a redo I do not want any experimentation. I want to cut my losses and go with the best system I know how to use. If I'm in your shoes it would appear to be CV as earlier recommended. If you want to be adventurous look at a 2k urethane system which is not really different from using CV. There are important things you need to understand about the difference in chemistry, but essentially it’s mixing part A with part B and spraying it.
From contributor Y:
I have to agree with Contributor A on this. It's not clear what your strategy is, but it sounds like you’re going with epoxy over an uncured, (for whatever reason) FDP, without knowing at this point if it's going to finally set up, as normal, and get hard? Lots of good info and suggestions here for sure, but first things first - check on the poly every week to see if the conditions are improving. If so you may as others have pointed out, not have a need to do anything but giving it more time ok?
Secondly, in the meantime you can take all the stamped info as to batch numbers etc. and call Minwax to have them check if there have been any drying problems reported about that batch, if not, then have them run a test with that batching number and see if it dries as all the rest ok?
Thirdly, find out just how your finisher did the applications to begin with. Was he rushing the finish, how many coats did he apply, and how close time wise were they? How did he sand them and with what and did he wipe the top down between coats with anything that might have affected the poly? Somethings minwax will probably ask of you anyway, among other things, so be prepared in advance.
Fourthly, after this is all done and you want to make samples up to try and duplicate what your now talking of doing, you must use the same material and as much as was used and same reducer if reduced at all to be able to know for sure. With all this there is still no guarantee that if the poly does finally dry hard after you have performed epoxy surgery etc.
I think everyone telling you to wait to see are the best answers as for now, with more time and better info all around. Then I think it will be safe to proceed if even necessary with the other steps recommended. Hopefully your client and yourself will be patient enough to see as each week goes by if there is a marked improvement in the film as to indentations.
From the original questioner:
Number one, to clarify I am the finisher, not a third party. I applied the poly myself, with about a 24 hour window between coats, with a slightly thinned first coat as a sealer coat (paint thinner about 20%). Each coat was lightly sanded with 320, dusted off with dry, clean rags, and re-coated. I am waiting a few more weeks before proceeding with anything, while in the meantime preparing a small sample copy back in the shop, duplicating what I have done already.
I'm already seeing a difference in the surface hardness, so thinking this is more a slow cure issue rather than a failure to cure. I will go ahead with the sample piece regardless, as I have another project coming up that requires the epoxy finish anyway and I want to gain some experience with it while in my shop. If my customer is adamant about moving forward with the epoxy over the poly (he doesn't want to see the top removed) I will do it with the understanding there are no guarantees we won't have to remove and start over in the end. His call, his money (he is a good customer, pays his bills). Either way, there is no rush. For now, I wait.
