Hi Mike

 

Most of the release problems don't have all that much to do with porosity as such but with reactivity.  Bondo is very difficult to have release easily unless it's sat around for a few years.  You can get sealers which as I had said, Chemlease make.  The Feather fill is at least as porous as the Bondo but doesn't have any problem releasing.  Remember that Featherfil is filled with microballoons and solvent so the solvent loss adds a lot to porosity that Bondo doesn't have.  The porosity on the microscopic level is small enough that the wax would easily fill it but still it bonds.  I applied a Hell of a lot of wax on a lot of plugs and molds and still had problems with release until I figured out what the problem was.  My point is that the bond is not mechanical (i.e. there are bubbles that get filled mechanically holding it) but is in fact chemical.  If you think back, when you waxed it up, I'd bet you were very carefull and waxed the Bejesus out of it several times.  Can you imagine that the paste wax youcarefully applied didn't completely fill in every pore and microscopic bubble?  In cases like that where you actually have trapped wax in a bubble, the release is easier since the laminate is actually sitting on a viscous solid rather than a surface coating of a few microns. 

 

Try the Feather fill or Duracoat over the Bondo, it's amazing for sanding and releasing.  It feathers beatifully.  It doesn't last long enough to do a lot of parts so it isn't a permanent mold repair or surface but it is awesome for a few parts. 

 

Some roughness can actually help release since as I said above, it can hold in a layer of wax to laminate on.  One of the easier to release surfaces is a non-skid surface for walking on as in a deck.  To make a dynamite non-skid, take ordinary gelcoat and mix in about 90% Cab-O-sil (fumed silica) and 10 % microballoons until it is the viscosity of Vaseline.  Add some styrene/wax solution into the mix to act as a surfacing agent.  8 cc/lb works pretty well.  Then take a paint roller and get ready to apply.  The nap makes very little difference so get the cheapest youcan find.  Short nap works well and takes less gel to saturate.  Catalyze the mix and stir well, then spread out a bunch of putty on a piece of scrap cardboard and roll in the gel until the roller is saturated.  You are now ready to apply to the part.

 

Using a notched trowel, spread an even coat of gel over the surface since IT IS THE THICKNESS OF THE GEL THAT DETERMINES THE COARSENESS OF THE NON-SKID, THE NAP DOESN'T DO ANYTHING.  More gel makes higher peaks and coarser nonskid until it stops being nonskid and becomes Velcro for skin. 

 

OK, you might not need to do non-skid for awhile but the point is that as coarse as it is, it always releases well when waxed. And it is a pain to wax!

 

Try Composite One in Sacramento for Chemlease or ask for something similar. You'll have to look them up, sorry.  You may be able to get sample quantities that go a long way.

 

 

 

Dan