Planex is burnishing

[Mbolton]

Hello, I have a Planex and a CT 36 AC with Granat abrasives in a variety of grits. I am doing two small remodel projects - one with brand new drywall and the other is existing 30 year old regular gypsum walls. Long story short, we want a Level 5, smooth finish in both areas so I skim coated with drywall compound both rooms, after sealing all the surfaces with Zinnser Gardz. The Planex works great for finish sanding inside corners and tapered and butt joints up to a Level 4 finish. I generally start with 180 or 220 grit Granat and up to this point in the process, all is well. Where my problem begins is when going back through the drywall work and doing touch ups  (missed scrapes or gouges, etc.) and especially after skim coating all the surfaces with joint compound, the Planex no longer efficiently grinds off the mud, it actually starts to burnish it, sometimes even putting a sheen on it like I was polishing it.

I can put a brand new Granat 180 disc on and it works as expected for about 3-4 vertical passes, floor to ceiling, before it feels like it needs to be replaced. The surface no longer has that dull, matte, chalky texture, instead it starts to darken and turn gray and starts to shine a little bit.  What's worse are the above mentioned patches done with a small 4" knife with a wipe on, turn  90°, wipe off action. These telegraph through the skimcoat, even though you can't feel them, as dark gray/silver and polished.  The only way to describe it is burnished.

I have played with different grits, different speeds and different suction settings and have yet to come up with a suitable combination. 120 grit will do it almost as fast as 180 grit and the same with 220 grit.

Has anyone experienced this?  If so, what am I missing?

Thanks!

 

[peter halle]

Welcome to the Forum!

I have about 5 minutes of experience with the Planex so I can't help you.  But I suspect that others will offer their thoughts.  You can also call Festool and talk to an application specialist who might be able to give some guidance.  The phone number is on your Planex label.

Peter

 

[tjbnwi]

Bucket mud or hot mud (Easy Sand/DuraBond)? Is the compound completely dry?

Using interface pads?

Are you sure there's paper on the pad? (don't be insulted, I've forgot to put a new piece on after pulling an old one off).

Tom

 

[Mbolton]

It's mostly bucket  mud, although I have used some hot mud a few places.  It isn't related to that or even these projects as I have seen it do it before.  I sprayed high build primer on the walls this past weekend and it does the same thing to it as it does the mud.  You get a few passes and it feels like the disc needs to be replaced.  And yes, there is a disc as I have tried new ones, old ones, different grits, etc. all to no avail.  If the discs were a penny a piece I would change them every 3-4 passes and all would be well, however, they are pricey!!  Oh, and, no, I do not use an interface pad.  I may look in to that.

 

[tjbnwi]

It's mostly bucket  mud, although I have used some hot mud a few places.  It isn't related to that or even these projects as I have seen it do it before.  I sprayed high build primer on the walls this past weekend and it does the same thing to it as it does the mud.  You get a few passes and it feels like the disc needs to be replaced.  And yes, there is a disc as I have tried new ones, old ones, different grits, etc. all to no avail.  If the discs were a penny a piece I would change them every 3-4 passes and all would be well, however, they are pricey!!  Oh, and, no, I do not use an interface pad.  I may look in to that.

I don't have the issue with my Planex. I've removed walls of knockdown and ceilings of popcorn that has been painted. Then skimmed and sanded.

Slower head speed?

Tom

 

[Mbolton]

When sanding out the skim coated walls I run it on about 2 - 2-1/2, anything higher and it burnishes faster.  :-/  The higher the suction the faster it burnishes, too.  The dang thing is so aggressive at 5 - 6 that I have only used it for popcorn, I couldn't imagine sanding raw mud with it that high.

 

[cblanton42]

    I recently filled in an exterior door opening and when I taped/mudded and sanded the drywall work inside I experienced the same thing you described, it was burnishing more than sanding, turning a darkish gray the more I sanded but I was sanding by hand! and had used hot mud with regular mud and just chalked it up to that. (and I believe that is your issue, the mud and or primer on the wall sometimes just won't sand right, I don't know why). 
      Have you tried using a wet sanding sponge?  That seemed to help me quite a bit with my problem, getting it wet, but I still had to fix those marks too, went with bucket mud and had no problems after that.

Good luck!! 
CB
     

 

[Mbolton]

Hmmm.... Ok, I will start to pay attention with hot vs bucket mud. I do go back and forth from time to time as needed, depending on what I am using, however, I didn't skim coat the entire wall with anything but premix (bucket mud).  I think I will reach out to Festool, too, and see what I am doing wrong. 

I found a good post on the interface pad here on FOG that leads me to believe I should have one, too.  But hey, can one have too many Festool products and accessories??  I think not!  [big grin]

 

[Nat X]

Hand sand it; does it do the same thing? If so, not the hardware.