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Author Topic: Gumming up of sanding paper  (Read 916 times)

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Offline JG

  • Posts: 39
Gumming up of sanding paper
« on: November 02, 2020, 01:12 PM »
When I sanded some exterior paint, the sand paper gummed up in spots with the paint.  I scraped as much as I could before I sanded and the sander was connected to a vac.  It was not a lot of gumming up, but enough to notice and enough to effect sanding.  I used 80 grit granat paper (not the mesh) and the speed setting on the ETS EC 125 and RO 125 (in rotex mode) was from 4-6. 

Is there anything I should change to resolve this issue?  Is there any way to clean the gummed up paint off the paper?

Thanks.

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Offline TwelvebyTwenty

  • Posts: 106
Re: Gumming up of sanding paper
« Reply #1 on: November 02, 2020, 01:50 PM »
Don't know what part of the world you're in to recommend a specific product. But research sandpaper/abrasive cleaning block/stick. Designed to work with belt sanders and rotary sanders, may need a slightly more delicate touch in RO sanders but should work.

Offline aloysius

  • Posts: 463
Re: Gumming up of sanding paper
« Reply #2 on: November 02, 2020, 08:39 PM »
Exterior paints tend to gum up abrasives rapidly when they melt.

There's a few strategies to try:
frequently clean abrasive/s BEFORE paint residues accumulate with a short piece of old PVC water pipe (the old black stuff is best).
try to keep things cool.  Don't sand in the hot sun.  Cold weather is actually better.  Don't lean on the tool too hard.  Allow the abrasive & substrate to cool frequently, perhaps when you're cleaning the residues off?

OR

Use the paint "melting" to your advantage.  Use drop-sheets to collect residues, & an angle grinder with a flexible backing pad & super-coarse abrasive to melt & "load-up" the abrasive with residue.  The friction will further melt paint on surfaces, removing it cleanly without harming timber substrates.  It's extremely messy.  Molten residues will be flung everywhere, hence the need for the drop sheets, but it's also far & away the fastest & (almost incredibly) the gentlest means of removing paint from surfaces without harming the timber beneath.  There's no exposed grit to abrade the weatherboards, as it's already covered with sticky melted paint residue.

This won't work with conventional sanders.  To achieve the high friction-induced temps required to melt the paint, you really need the speed & power of an angle grinder.
FOG-wit since '95:  Some say since birth...

Offline wynne city works

  • Posts: 1
Re: Gumming up of sanding paper
« Reply #3 on: December 25, 2020, 02:33 PM »
Use the RO 125 in Rotex mode for first pass and go SLOW ( the slower you go the faster the job goes) - run some Granat 60 (or lower) on speed 1-2 and keep it moving. If you hesitate in a area for long heat will build up and melt the material you are trying to sand away. The lower grit also allows more space between the grit for the sanded material to move through to the suction holes. After you remove 90% of the material on speed 1-2 in Rotex mode you can switch to Dual Action mode on speed 4-6 and clean it up done to fresh wood.


Offline Crazyraceguy

  • Posts: 225
Re: Gumming up of sanding paper
« Reply #4 on: December 27, 2020, 08:25 AM »
Years of working in an autobody shop taught me two things about clogging sandpaper.
Assuming that you are using quality paper in the first place....one of two things is happening.
Either the material to be sanded is not sufficiently dry or the paper is too fine.
Also the thickness of the coating to be stripped makes some difference. Thicker coatings or more layers require a more coarse grit. If the substrate is delicate, with multiple coats, use a finer grit on the last layer.
I wouldn't start with higher than 60 grit and if it clogs, go to 40. Don't go hog wild with the 40 grit though, you still have to get those scratches out later. Get the bulk of the finish/paint off with it and ease into 60 and then 80.
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Offline Alanbach

  • Posts: 635
Re: Gumming up of sanding paper
« Reply #5 on: December 28, 2020, 12:24 AM »
Sorry for the late arrival, I just saw this thread for the first time. Have you ever tried Festool’s Saphir sandpaper. It works amazingly well on painted surfaces.

Offline fuzzy logic

  • Posts: 373
Re: Gumming up of sanding paper
« Reply #6 on: December 28, 2020, 08:16 PM »
I agree with Alanbach wrt to Saphir. 

Recently I came across a short length of old heavily multi-layed oil based painted trim, that I used, donkeys years ago, to familiarise myself with what I thought about the performance of different abrasives.

On that piece of trim, I had used 60 grit 'Cristal', 80 grit Saphir, 40 grit Brilliant and 50 grit Rubin. 

Running my fingers over the surface of the Saphir surface, was slightly taken aback at how smooth it felt. Quite impressed actually. 

But, I really, really miss the Cristal abrasives (RIP).  Ok, the backing was little 'delicate' but did a good job.  Once in a while, I come across a disc or two of Cristal - perhaps I should 'frame' them for future generations to wonder at...

Richard (UK)
Decent people do the right thing - always?