old finish new sander

[paulgordon]

Just bought the 5 inch sander, old sander now looks so old and lonely on the shelf.  Working on a very old door with a finish that I think is alcohol soluable.  However, after a few minutes disk is gummed up. I can remove this easily from the disc, however, it really slows things down.  Using 50 and 80 & 120 grits. 

Any advice other than to remove as much of the old finish as possible chemically before sanding?  Paint does not seem to do this to the discs.

 

[ohkipp]

Sounds like some really old varnish. This will clog up just about any paper I know of. Other than chemicals which might be an option I would try  a paint scraper first to break up the surface as much as possible without scratching the door to deep. Then go over it with some 80. You have picked a tough job but it can be done. Patience will work everytime.

 

[Tim Sproul]

a finish that I think is alcohol soluable. 

Shellac is a common film finish that readily dissolves in alcohol after drying/curing.  Shellac is temperature sensitive...get it warm and it gets very gummy/soft and you get the corning issues you're observing.

1.  Scrape it off (as mentioned already).
2.  Slow down the sander and move it around quickly.  Move the sander a lot faster than you would for surface prep of a new project.

 

[Lou Miller]

Just bought the 5 inch sander, old sander now looks so old and lonely on the shelf.  Working on a very old door with a finish that I think is alcohol soluable.  However, after a few minutes disk is gummed up. I can remove this easily from the disc, however, it really slows things down.  Using 50 and 80 & 120 grits. 

Any advice other than to remove as much of the old finish as possible chemically before sanding?  Paint does not seem to do this to the discs.

I agree on scraping and especially agree on slowing the sander down. I strip a lot of old finishes with my sanders. Sure, I get some gumming of the paper, but not a whole lot. I scrape anything I can first. Then I set the sander to either the 1 or 2 speed setting.

One thing you didn't mention was the type of paper you're using. Based on the grits you are using, I think you're using Rubin (brilliant comes in 40 and 60 grit, not 50)? Rubin is great paper for bare wood. However, its not all that good to sand any type of finish with as it'll clog much faster (no need to tell you that though). The Brilliant has an anti-static coating on it that does make a difference in an application like yours. While the scraping and slowing the sander down will help, you still need to use the right paper. Go get yourself a box of 40 or 60 grit Brilliant to remove all of the finish with. Once the finish is gone, then switch over to your 80 and 120 grit Rubin. You'll be much happier with your results.

 

[Dave Ronyak]

I struggled with a similar problem - repairing and refinishing several mahogany veneered interior doors that were varnished about 50 years ago.  I did not have much success with any chemical strippers that I tried, and I tried several.  All of the chemical strippers softened the old finish and enabled most of it to be scraped away, but the residue that remained rapidly gummed up any sandpaper that I tried, despite many repeat treatments with chemical stripper and the manufacturer's recommended final wipedown solvent, etc.  For whatever old finish was on my doors (my guess is alkyd varnish over shellac), I decided it was definitely better overall to simply sand off the old finish.  Because they were veneer and I had no replacement material except as salvaged from one of the doors that I sacrificed and replaced with a new oak door, I used only 80 grit and up with my RO 125 to help prevent sanding through the veneer.  As others have said, the keys to minimizing loading of the abrasive paper are to use the right type of paper and to turn down the sander speed.  Even so, little swirls of ?melted? finish would build up on the sanding disk.  I soon learned I could quickly pop them off using a simple scraper (~1 1/2 inch HD putty knife) held at the correct angle with the sander powered at very low speed.  Be careful that you don't snag the tool and end up cutting yourself, since you will also be making that scraper very sharp as you use it like this!  From my experience, I somewhat disagree with others recommendations regarding type of abrasive.  For my situation, to my surprise, Rubin worked best, not Brilliant as is likely for most.  I know that my old finish was not shellac, or at least not pure shellac, because when I wetted it with denatured alcohol, it crazed more than softened.  You did not state If the old finish is clear (amber?) shellac/varnish, but I am guessing that it is.  I believe the old finish on my doors were likewise.  I intentionally left some of that old finish on my doors - to help fill in mostly the pores of the mahogany veneer, and began application of new finish with a wash coat of dewaxed shellac (Zinser's) followed by a 2 -3 coats of polurethane (all solvent based).

Good luck!

Dave R.

 

[semenza]

Hi,

      The Cristal is very good at not loading up , also.

Seth