rinconmike Posted October 11, 2020 Report Share Posted October 11, 2020 Hi. We have been working on a cubby system for the local High School band room to store the instruments as part of an Eagle Scout Project. Been working on it for 7 months. The cubbies are made out of 3/4" Baltic Birch Plywood and we decided to use Waterlox Urethane to finish. We have six of these with varying cubbies. Four of them have overall dimensions of are 27" wide, 29" deep, and 72" high and the last two are 78" high. Attached is a photo with one that has the most cubbies and also one showing the six together. We have done the three coats of Urethane over the entire cabinet and a fourth coat on the bottom and side inside of each cubby. Each coat was done around 24 to 48 hours apart (we first did all coat 1, then coat 2, then coat 3). Since it is more than 12 hours between coats, we have been lightly abrading. Initially we were abrading with steel wool. We then change to a 3M maroon pad (320 grit). Also, the recommended application rate is 1 quart to 125sf however, based on what we used, we are closer to 1 quart per 225sf. I believe this is due to how much vertical surface we have and if we went any heavier, we got drips. Now that we are done, and I am reading more. I am concern we did not abrade enough between coats. I wanted to abrade more but since I tend to overdo things my wife (who did most the finishing) wanted to stay on the lighter side. The scouts did the abrading with our supervision. The abrading was light with probably 4 or 5 passes with the steel wool or maroon pad (when we changed to the pad). Rubbing a finger after abrading there was a small amount of dust on the finger. Some areas more than others. We then cleaned with a vacuum and tack cloth and then applied the next coat. Although we are done and no going back, I am concerned that if we did not abrade enough we might have an issue with the finish and looking for some input on thoughts if we may have a problem with the finish peeling at some point that we will have to address later. I should have looked for input sooner. This is the first big project we did. The scouts were great in participating on assembly and finish. Just hope there are no issues with the finish. thanks for reading. Mike 10 Cubbies 72in Tall.jpg https://www.dropbox.com/s/kf0fh4yh7d43khm/10%20Cubbies%2072in%20Tall.jpg?dl=0 All Six Cubbies.jpg https://www.dropbox.com/s/6s0i4dqakcgvyzy/All%20Six%20Cubbies.jpg?dl=0 Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted October 12, 2020 Report Share Posted October 12, 2020 While that is considerably finer than I usually sand between coats of poly, I seriously doubt you will have adhesion problems from it. In my personal experience, making the surface "clean" between coats is more important than making it "rough". Removing dirt and oils aids adhesion as much or more than adding "tooth" to the surface. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted October 12, 2020 Report Share Posted October 12, 2020 This is going to be a case by case sort of issue that none of us can really comment on without being there. Urethane does not burn in, so if there is any chance curing to gloss happened on the surface, you are just knocking the gloss back as well as providing some mechanical tooth. Four or five passes are fine in my experience, but the whole surface should be treated evenly per the manufacturers specs. If there is a problem, it’s always best to follow those specs. Quote Link to comment Share on other sites More sharing options...
rinconmike Posted October 12, 2020 Author Report Share Posted October 12, 2020 thanks for the replies. We used the semi-gloss urethane. I am not sure if we got all the gloss off. I thought we were following the directions when we did a light sand but concerned we are too light. So if there is an issue, would peeling happen right away or will it take time or no way to tell. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted October 12, 2020 Report Share Posted October 12, 2020 Unless the surface has a really oily spot, I doubt you will see any peeling right away. More likely is that the finish will begin to fail earlier than it might, otherwise. At a guess, I'd say if 30 days go by without an issue appearing, you're probably good for the long haul. Considering the application, damage from typical use in a school setting is probably going to overshadow any failure related to your finishing methods. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted October 12, 2020 Report Share Posted October 12, 2020 Full disclosure, I am a band director by day right now. The wear areas are the top corner of the shelf. I’d recommend metal edge guides. The second most wear is scuff along the bottom as feet fall off of cases. Just additional thoughts as I am around those cabinets in their use every day. 1 Quote Link to comment Share on other sites More sharing options...
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