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I'm putting together three big desks to use with my children in our new work and study room. The table tops are butcher-block beechwood, and I finished them with a two component post-catalyzed lacquer by the Swiss company Ruco. (Product: RUCOPUR Aussen- und Innenlack, Acrylpolyurethanharz / aliphat. Isocyanathärter, 3:1 mix with catalyst.)

I sprayed with a Warner 550 HVLP set I bought last week. (That turned out more difficult than I expected - very tricky to use with small amounts of lacquer.)

After spraying three coats and sanding in between I went to work at rubbing out. The results are good for the most part, but in a few places at the edge of the work, some water from the wet sanding got into the wood, which swelled up. In about 4 spots I ended up sanding through the wood at these swollen spots, creating a bald patch. (These have developed in particular around the holes I drilled to run computer cables through the table.)

I'm trying to figure out what to do about those patches. I'm planning to let the whole thing dry out for 24 hours, then sand down the swollen areas (assuming they don't receed), mix a small amount of lacquer, apply with a small paint brush, then re-sand. Will this work? In particular, will I be able to sand the new lacquer back so that it blends in with the rest??

I'm also thinking it might be smart to dilute the lacquer with a bit more solvent than before (maybe 40% instead 20%?), to make sure it doesn't pile up too much.

Or is there a better way to tackle this?
 

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You need to sand hole edges flat before applying the finish since the drilling as well as air moisture can cause the surface to swell. It's a good idea to apply finish inside the hole. I would sand out the tops and start applying lacquer on the whole top just as before, no extra thinner. Things will blend in fine. Spot fixing isn't the way to go. Don't try to skimp when filling the gun, you need enough product so it can siphon adequately.
 

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Rats - That's what I thought ...

Thanks for the tip.

I was hoping I wouldn't have to respray (and buy more lacquer!) - but ah well!

A guy at the varnish shop told me that I've probably been too skimpy with the material, which lead to an uneven, rough finish and a whole lot of sanding and holes. Anyway, I've sanded down the swollen surfaces and used a brush to seal up the open, vertical edges (particularly the sides of the drill holes).

I'll buy more lacquer today and re-spray all three tables.

I'm having trouble getting my Wagner 550 under control - in particular, I can regulate the spray power, but I'm not sure what setting I *need* - a hard spray and move quickly along the tables or more of a slow mist and move slowly.
 

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Thanks for the tip.

I was hoping I wouldn't have to respray (and buy more lacquer!) - but ah well!A guy at the varnish shop told me that I've probably been too skimpy with the material, which lead to an uneven, rough finish and a whole lot of sanding and holes. Anyway, I've sanded down the swollen surfaces and used a brush to seal up the open, vertical edges (particularly the sides of the drill holes).

I'll buy more lacquer today and re-spray all three tables.

I'm having trouble getting my Wagner 550 under control - in particular, I can regulate the spray power, but I'm not sure what setting I *need* - a hard spray and move quickly along the tables or more of a slow mist and move slowly.
At this point it wouldn't hurt to try the spot fixing. To brush the lacquer you would need some retarder to extend dry time and make it flow. Yep...something else to buy. But in lieu of that, try just reducing the mix.

Getting your application to a good coat, is sort of a mix of movement speed, air flow, fluid flow, pattern, and distance from the subject. Before doing the tops all over again, I would do some experimenting with the gun and some plain lacquer thinner. Use some cardboard as a subject. Make sure you have a lot of light to get a "glare" off your spraying path so you can see how wet it's getting.








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Hey, thanks - that was mighty quick!

Full confession mode: I actually tried the touch-up two days back; yesterday I sanded down. That worked pretty well, actually, though it took about 2 hours works. Though the touched up areas came at fairly lumpy, I was able to sand them down to level. However, I then took a shot at some other uneven patches and ended up opening a few new holes. Also, I found that some of the swollen places weren't really flat.

So I'm ready to do this right now.

One thing: what is the surface supposed to LOOK like, immediately after I spray it correctly? Should it be completely smooth? Almost a puddle? I'm thinking (always dangerous in my case!) that I could add more thinner this time a spray it quite wet and puddly: since the table tops are flat, it's not like I'm going to get major runs ...

I was originally trying to spray with very small amounts of lacquer. The company chemist told me on the phone that I should buy three whole cans (mixed with catalyzer, about one liter each) for three tables (160cm by 80cm). However, the first guy I talked to at the paint shop said I only need one can, maybe just a little of the second. I think I should have followed the company guy's advice ...

Mike
 

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OK, I've now re-sprayed all three table tops.

They're looking a lot better this time; however, there are sill some sections with some orange peel effect as well as some rough spots - that come through of a kind of sparkly effect. There are also about three gnats that decided to fly in and get stuck.

I have enough lacquer left for one final spray with about as much lacquer as this last time. I'm wondering a couple things:

1) How much sanding I should do before I spray the final layer?

2) Am I trying to get rid of all the orange peel and/or rough spots and/or gnats or am I just creating a new kind of roughness for the next layer to stick? (I mean, the gnats definitely come out - but do I want to sand until there's no sign of the bug?

3) How fine? Just 240 paper or something finer? (I have up to 2500!)

I've included a couple pictures; however, I turned out to be very, very difficult to get the imperfections to show up in a snapshot. Stil lthis may give a hint.
 

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I would use 320x before your final application. You should sand out what you don't want to see. If you catch those illegal immigrants soon enough, you can pick 'em out with a needle. Your last coat would lay out better with using a bit of retarder. I can get a very smooth coat with just an "off the gun" application.

About the retarder, it doesn't take much. If you use too much your lacquer will dry but will take a while.








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