Stripping FUD

[BCR751]

When this shell was painted, it showed a very distinct mottling over most of the surface.  It is a FUD printed shell from Shapeways.  I believe what happened was that I wasn't diligent enough when sanding off the horizontal print lines which resulted in an uneven surface and the subsequent mottling of the paint.  Where the shell was sanded smooth, the paint looks fine.  I have another similar shell, printed at the same time, that is perfect and took the paint with no mottling.  It must have something to do with how the piece was oriented during the printing process.



Since there is no way to fix it at this point, I will have to strip the paint and start over.  What should I use to strip the paint so as not to screw up the shell?  I have on hand ELO and 91% isopropyl alcohol.  I've never tried to strip paint from a FUD item before so I need some direction.

Doug

[Steve S]

Don't know about the stripping, but did you prime first?  On the printed models that I've painted, I primed first, then sanded until the resin started to show through.  Basically the primer paint fills in the little nooks and crannies.  Then I primed again and got a smooth finish.

The corrugated panels on your model are going to be difficult to sand, though.  Is the roof corrugated?  Or is that just the layering from the printing process?

Steve S

[BCR751]

Steve,

I did prime it prior to painting but I only sanded it before the primer  was applied not after.  That does sound like a good idea though.  Hopefully someone will chime in with a paint removal suggestion because I think that will  be required.

Doug

[C855B]

I have read somewhere (here?) that 91% iso soaks are bad news with FUD/FXD, breaking down the material. I certainly don't know that for a fact.

But tell you what... I have some sacrificial FUD shells that were guinea pigs for various paints I was testing. Let me grab the worst one, dunk it in some 91% and let's see what happens.

[C855B]

91% iso alcohol? FUD/FXD? And the answer is...

ABSOLUTELY NOT!!!

Shell warped within 20 minutes. Keep alcohol away from FUD.

[Wutter]

Shell warped within 20 minutes. Keep alcohol away from FUD.

+1 for this. Anything made with FUD and FXD that I've tried to strip in isopropyl has gone badly.

Would it be possible for you to use a fine sandpaper (1000+ grit)  to sand the smooth areas and possibly even some of the corrugations. A knife or scoring tool can be used to lightly rescribe the corrugations prior to repainting. This would make the base layer of silver you have on there work similar to a primer although it probably isn't that thick and you'll have some sand through in spots.

[Chris333]

Will acetone strip paint?

[peteski]

Will acetone strip paint?

Yes, and it will also attack FUD as bad as alcohol (acetone is much more potent solvent).

I wonder if anybody tried the lye-based strippers (like Castrol Super Clean - the purple stuff)?

[Chris333]

I asked because before Bestine all I used was acetone. And still now when parts remain sticky after Bestine I use acetone to make the parts bone dry.

[peteski]

I asked because before Bestine all I used was acetone. And still now when parts remain sticky after Bestine I use acetone to make the parts bone dry.

If your FUD does not have thin cross-section parts on it and the FUD object is in contact with acetone only for a short period then they will survive. But if you dunk the item in acetone for a longer period, the thin cross-section parts will soften up and will brake under slightest pressure.  I once used lacquer thinner (which contained a rather large percentage of acetone) to clean the wax off some thin parts and they disintegrated after the rinse when I was handling them.

What type of paint was used?  If it was water-based then maybe scrubbing the body with ammonia or Windex (which has ammonia) would remove the paint?

[BCR751]

What type of paint was used?  If it was water-based then maybe scrubbing the body with ammonia or Windex (which has ammonia) would remove the paint?

The paint used was an acrylic, Vallejo Air chrome. 

I'll try the ammonia but if that doesn't work, what about Easy Lift Off or good 'ol brake fluid?  Any chance those would work.  I know ELO has some alcohol in it but not sure about the formulation of brake fluid.  Maybe I'll just have to try them out and see what happens.

Doug

[BCR751]

Update:  The ammonia had absolutely no effect.  I then tried Easy Lift Off.  Covered the shell with it and watched it closely.  After about 30 minutes, the styrene part that I had glued to the shell showed signs of the paint crinkling.  No crinkling on the FUD.  Left it for another 15 minutes.  The paint literally fell off the styrene part but still no movement on the FUD.  I then put the shell under warm water, used some dish soap and started scrubbing with a medium stiff toothbrush.  All the paint came off the styrene part beautifully. However, on the FUD, the paint became a sticky sludge and would not come off.  The more I scrubbed the more sticky and gooey it became.  It just would not come off the FUD.  Finally, more scrubbing started distorting the FUD so I gave up.  I've essentially ruined the shell.

So, for educational purposes, do NOT use ELO or ammonia when trying to remove paint from a FUD printed item.  No idea what would work on this stuff.

Doug

[peteski]

Thanks for posting the results and sorry that the shell is ruined.   The other stripper to try could have been lye-based (the Purple Stuff I mentioned earlier).

[Mike C]

Couldn't resist .......

[Chris333]

Well now that it's ruined you can test all sorts of stuff on it!