Replies

1. 
   KeithNewton | Sep 09, 2005 03:09am | #1

   Couple of tricks. If you have or can get one of the air nozzles that has a hose barb for a vinyl tube to siphon solvents for cleanup, If you can have it handy whenever you are spraying, with a little piece of vinyl tube on it, you can suck a sag up with it before it starts to set without having a big smear like wiping creates. You may still have a thin spot, to deal with, but less of a pain than a run.

   If you don't find it until later, sanding will usually cause it to wad-up or roll up while you sand through the thin area around it.

   I like to take a single edge razor-blade, and with a small burnisher, like the smooth shank of a drill bit, laying on the bench-top. Start with the cutting edge at about 45* and with a back and fourth rolling motion while bringing the blade up to 90*, you will now have a razor sharp scraper with a bur rolled over, that you can easily flex a little bow in. I like to draw it toward me with my thumbs under, and one index finger on back, I find I can shave it down to pretty close to level with the surface around it. This doesn't work if it is too tender, you will have to wait until it is pretty firm.

   Good luck, I would like to hear back from you if it works for you. K

2. 
   Rich14 | Sep 09, 2005 03:20am | #2

   Su,

   Not only CAN you sand the shellac, you MUST. A shellac finnish consists of many thin coats. While each coat will adhere perfectly to the previous, with no sanding at all, the result will look awful, because the hills and valleys of the finish (a normal result) have not been leveled. You have added the additional problem of drips which must be brought down perfectly smooth with the surrounding area.

   Level sand the first coat lightly with 320 grit on a felt or rubber sanding block. The goal eventually is to obtain a completely uniform matte surface of the shellac before the next coat. But you can't do this with the first leveling. Just take down the highest peaks with light pressure, leaving the shiny valleys. The drips need to be completely leveled. Make sure you wait long enough for the shellac to have dried. Shellac is a joy to sand, but it must be dry. Usually 24 hours is plenty.

   With each succeeding coat, the leveling becomes easier and more uniform. The shiny valleys eventually dissappear. The sanding should produce a fine, dry, powder of shellac. After 3-4 coats of finish and sandings, the surface should be uniformly matte with the 320 scratch pattern. You can stop at that point, or apply several more coats, then go to finer abrasive, such as 400, 600 grit, 4-0 steel wool, then automotive rubbing compound, polishing compound, swirl removal, stopping at the grade that pleases you.

   Short of the swirl remover, the abrasives produce a finer and finer matte surface. Swirl remover produces a final, glass-like finish.

   And that's shellac.

   Rich

   
   

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   Edited 9/8/2005 8:22 pm ET by Rich14

3. 
   Paul_Snyder | Sep 09, 2005 06:10am | #3

   The approach I use to eliminate runs and sags is to cut or scrape them down and then sand them level to blend in.I use a single edge razor blade and bend it slightly to limit how much of the blade contacts the surface. Then holding it at a low angle, I slice the thickest portion of the run or sag from the finish if it's soft enough. If the finish is hard, then hold the razor at a steep angle and pull it towards you to scrape the run/sag. Once the bulk of the surplus finish is removed, sanding the area lightly levels it nicely so that the run or sag is no longer noticeable.

   View Image Bowed Blade

   View Image Run Scraped Down

   View Image Sanding Completes the Repair

   Paul
   http://www.finishwiz.com

1. 
   Kevin | Sep 09, 2005 07:21am | #4

   Very interesting variety of responses! Interesting mostly just to see how different finishers tackle the same exact problem.

   I've always done it the same as what Paul described except that I'll usually wetsand using #320 and mineral spirits rather than dry sand. I used to dry sand after scraping. But, I've found that wetsanding helps me to get it flatter.

   Edit: By flatter I mean that it's easier and faster. The finish doesn't have to be as dry or as thick. And if it's over veneer, the veneer doesn't have to be as flat. Where I work almost all the veneer is hand-laid. So, it tends to be lumpy and wetsanding allows me to work the run or sag with much less risk of accidently burning thru somewhere. 

   One of the beauties of wetsanding a run or sag in shellac, lacquer or conversion varnish with mineral spirits is that it doesn't have to be nearly as dry as it does to effectively shave it with a razor.

    

   Edited 9/9/2005 12:30 am ET by Kevin

4. 
   WillGeorge | Sep 09, 2005 07:35pm | #5

   shellac..

   Just me... Shellac is so forgiving... Depends on how bad the sags are but sanding (take your time) will correct almost all of it...

   Use the finest grade and see how it goes.. If not.. use the next corser grit and finish with the finer grit..

   Yes it may need another coat but keep it 'LIGHT'...

   WELL, JUST WHAT I WOULD DO!

5. 
   philip | Sep 10, 2005 01:05pm | #6

   SuRje,
   I just level them with a cabinet scraper and then go to sanding etc. I don't sand them flat because I am a scrooge with the sand paper and I always try to minimise the necessary sanding.
   This seems to easy-have I missed something?

   Philip Marcou
1. 
   WillGeorge | Sep 10, 2005 07:10pm | #7

   I am a scrooge BUT I just LOVE Christmass

1. 
   Biscardi | Sep 10, 2005 11:14pm | #8

   I've had good sucess with shellac out of aerosol cans. I think the key is to hold the can far back and don't be afraid to waste some shellac. If you get right up on it, or don't keep the can moving it, builds up too fast and drips/runs.

   Frank