Festool sandpaper loads up extremely fast. What's wrong?

[Kodi Crescent]

I'm building a toy box out of plywood.  I've been painting it with Krylon spray enamel, and sanding between coats.  I plan on putting several coats of paint on so that it has a durable finish.

I'm sanding using the 150/5 with 320 Brilliant, hooked up to a CT-22 set on full suction.  I can put a new piece of paper on the sander, and within 15-30 seconds of sanding the paper is well-coated with large, flattened globules of paint.  If I keep sanding with the loaded paper, the little globules get smeared into the surface.  I have to change paper about every 20 seconds to avoid this.  Its the fast lane to the poor house.

Does the paper normally load up this fast?  I thought Festool paper was supposed to last a long time.  What am I missing?

Thanks!

 

[peter halle]

Enamel paints go thru a drying process.  I suspect that your paint was not fully cured.  Curing may take several days based on individual conditions.  Wait longer before sanding.

Peter

 

[vwdave]

Well I don't finish my work so I can't comment about the paper but you should not be using the vac on full suction it should be almost to the least amount of suction

 

[BobKovacs]

As Peter said, the problem isn't with the paper- it's with the paint. Spraycan paint isn't going to cure out very fast, so either you're going to have to wait days between coats to sand, or lay the coats on close enough in time that they basically melt the old paint into the new, eliminating the need to sand.

 

[mouppe]

I used sprayed enamel paints once on a model car. I am not exaggerating when I say it took WEEKS to cure. If I were you, I would strip the paint, and redo it with lacquer. The Tamiya spray cans are excellent- just wear a respirator when you spray. The lacquer dries hard within an hour, and you can respray.

The advice about turning down the vac suction is good advice, but it is probably not what is causing your sandpaper to clog up so quickly. The paint has not cured properly underneath the outer layer.

Forget enamels. Go with lacquers.

 

[mastercabman]

Like others said,wait until the paint dries,and/or sand lightly by hand.

 

[peter halle]

Like others said,wait until the paint dries,and/or sand lightly by hand.

Very valid post - in my mind.  Enamel paint cures from the outside in.  You might be able to scuff and lightly sand then spray again.  Imagine an M&M.

 

[Kodi Crescent]

Okay, the paint not being cured makes sense.  I was sanding 24 hours after painting.  This project has been quite the learning experience, and taken far far longer than I anticipated.  I'll lightly hand sand so I can get it painted and finished and use a different paint next time.

Thanks!

 

[Ken Nagrod]

I agree on both points that turning down of the suction is a good thing, but I also believe that the main reason is what others are saying, the paint isn't curing by the time you're sanding it.

From my training in the automotive refinishing business, lacquer cures by evaporation of the carrier - lacquer thinner and enamels cure through a chemical process (oxidation) - the oxygen in the air makes and keeps that process going, usually fully air cured by 30 days or as quick as 15 minutes under infrared medium to long wave.

I believe the problem you're having is exacerbated by the fact that each coat of paint hasn't cured enough by the time you go to sand it, and by sanding it you open it up to a less cured depth like Peter referred to and then you put another layer of paint on top of the uncured paint trapping the layer beneath so it takes much longer for the underlying layers to cure.  Then you sand again actually pulling off that lower uncured layer that has the outer paint layer attached to it.  That's why the quick buildup on the sandpaper.  That's also why paint instructions say to re-coat within a certain amount of minutes or wait a certain amount of hours, because that next coat you put on is supposed to either chemically blend in with the previous coat OR go on top of the previous coat that has had sufficient time to dry so you're not trapping an uncured layer.

If you can get some heat lamps or make some up yourself using ceramic sockets for the infrared heat lamps, that will definitely speed up your project and once hardened, is stronger than a lacquer finish, but not as easy to repair should you need to.

 

[5280]

Like above:
Cure the paint
Back off the suction so the sander floats. I would guess like said, near the lowest setting. But floating not sucked down.

 

[Michael_MA]

I agree on both points that turning down of the suction is a good thing, but I also believe that the main reason is what others are saying, the paint isn't curing by the time you're sanding it.

From my training in the automotive refinishing business, lacquer cures by evaporation of the carrier - lacquer thinner and enamels cure through a chemical process (oxidation) - the oxygen in the air makes and keeps that process going, usually fully air cured by 30 days or as quick as 15 minutes under infrared medium to long wave.

I believe the problem you're having is exacerbated by the fact that each coat of paint hasn't cured enough by the time you go to sand it, and by sanding it you open it up to a less cured depth like Peter referred to and then you put another layer of paint on top of the uncured paint trapping the layer beneath so it takes much longer for the underlying layers to cure.  Then you sand again actually pulling off that lower uncured layer that has the outer paint layer attached to it.  That's why the quick buildup on the sandpaper.  That's also why paint instructions say to re-coat within a certain amount of minutes or wait a certain amount of hours, because that next coat you put on is supposed to either chemically blend in with the previous coat OR go on top of the previous coat that has had sufficient time to dry so you're not trapping an uncured layer.

If you can get some heat lamps or make some up yourself using ceramic sockets for the infrared heat lamps, that will definitely speed up your project and once hardened, is stronger than a lacquer finish, but not as easy to repair should you need to.

Excellent explanation Ken  [thumbs up] 
This is another day on the FOG with a great learning experience for me

kind regards, Mike

 

[fdengel]

Like above:
Cure the paint
Back off the suction so the sander floats. I would guess like said, near the lowest setting. But floating not sucked down.

I use about 1/3 power with my RO 150 and find that suits me fairly well for a large flat surface with the sander not on its side or anything (would probably turn it up if I were sanding as if against a wall or ceiling...), but the 150/5 might be different?

+1 on the excellence (and educational value) of Ken's explanation.

Another option might be to use a paint that dries/cures faster, something like Createx sprayed through an airbrush?  Many airbrush paints (when used with an airbrush) seem to dry very quickly compared to other methods, because of how thin the layers are, combined with the volume of air that gets mixed with the paint during application.  In fact, if you read around, you'll find stories of the paint bouncing off the workpiece when the brush is held too far away, because it had dried in mid-air before hitting the surface!

Of course, with this comes the need to practice and get a feel for using and cleaning the brush; an air source, possibly a moisture trap, etc...

 

[Ken Nagrod]

Thanks Mike & fdengel.

Kodi and anyone else that might find this helpful, here are some pictures of what I was referring to about the infrared heat lamps.

The first one is the cheapest, probably less than $20 for the short wave infrared bulb and the ceramic socket with clamp.  I had dropped mine long ago, broke it and used JB Weld to repair it.  Still going after maybe 15 years.  Just be careful, because you have an exposed bulb that gets very hot.

Second picture is really a body shop version, but there's no reason you couldn't get one and use it for woodworking finishes.  It's a medium wave quartz tubed infrared unit with a timer.  It heats a 3x4 foot area and this is the high intensity model that's around $500, however Infratech makes some lower output models that are less expensive if that suits your needs.

I'd advise getting an infrared non-contact thermometer so you can keep an eye on the surface temperature of what your heating.  If you get these (especially the high output model) too close to the surface your heating, you can melt it or catch it on fire.

Infrared penetrates thru the layers to heat from the bottom most layer up.

 

[fidelfs]

If I use a heat lamp, how long do I have to use it, si it is cured for sanding?

What would be a safe temp. Before I have to turn off the heat lamp?
???

 

[Ken Nagrod]

If I use a heat lamp, how long do I have to use it, si it is cured for sanding?

What would be a safe temp. Before I have to turn off the heat lamp?
???

How long you have to use it for, I can't answer without first knowing what coating you put on that you're trying to cure and what it's on top of, like wood, metal, etc.

Probably the best answer will either come from the manufacturer of the product you're trying to cure or a test area that you do.  What I mean by the test area is you heat it for a certain amount of minutes, maybe start with 45, then let it cool down for at least 15 minutes, then try sanding and see what happens.  If that works, then try less heating time or if it doesn't work, use more heating time, but always allow plenty of time to cool down before handling and sanding.

The temperature of the surface you're heating should remain constant throughout once it comes up to temperature.  When you first turn on the heat lamp, it takes a little time to build up temperature.  What varies the temperature is the distance your heat lamp is from the surface you're heating.  USUALLY you shouldn't go higher than around 150 degree F range while aiming an infrared thermometer at the heated surface in multiple areas.  You might see different temps in different areas and need to move the heat lamp around to cure all of the areas fully.  It's always best to start at a greater distance, check your surface temps and move it a little closer at a time if necessary, always rechecking the temps.  Look at what the surface coating is doing.  If it's smoking or burning or bubbling, it's too hot = too close with the heat.