O
Overspray
Bob - Very good points no denying that and thanks for the feed back. Yet, the goblets of paint hitting the substrate surface will never be as refined from a HVLP gun as that from a truly aspirated conventional gun. Identically repeatable results between the two systems ? - No, Physically by their design natures impossible. Yet yes similarly obtainable results can be gotten via a HVLP wielded only by a gun sprayer that has earned his/her abilities obtained only though hours of applicable internal cerebral tweaking and mastery of application.= If that makes sense Grasshopper :')
rustover - Long Winded Version 1.0 ..
There is nothing really wrong with the old tried and true way of 36 grit biting into clean raw clean metal, ( Mechanical Bond ) thereby trenching a foundation foot hold for the primer. Remember when using a true Pure Epoxy Admixture which consists of a very high quality resin / amine ratio coupled to a low solvent concentration blend mix level with no talc spores for sandability, and resulting in a final admixture requiring no induction times, which truly exotherms, ( heat generated from chemical bonding actions ) ; The ability to obtain a true Chemical Bond when using two different chemical yet compatible commodity compounds ( ie. epoxy to filler ) , then Yes the matter of spraying the epoxy first onto the virgin substrate prep'ed metal then applying the filler before the epoxy completely kicks ( exotherms ) to get a true full chemically bonded adhesion is obtainable. Because one is enhancing and achieving an overall bond known as a pure" Chemical Bond" and not just a pure " Mechanical Bond " . Now with that said, using a "compounded" Epoxy admixture system ( Sandable Epoxy Primers with varying high solvents ratios with various micros talc concentrations for sandablitly ) this truly achievable Chemical Bond quality decreases in real time linearly in relationship to the varying degrees of these compounded epoxy ratios used.
In other words, getting a truly chemically set rock solid effective chemical bond with these products is so-so. So in our cases, a properly executed 36 grit into metal prep would be just as similarly effective as applying filler to a 12 hour old kicked epoxy spray mechanically bonded to the metal surface that has already had it's initial active chemical exothermal actively completed.
In rebuttal to this, you will then hear folks attempting to warn and tell you, a repeatable mantra chant that dictates it is most important to Epoxy first onto the metal substrate surface ( A Mechanical Bond by the way ) before applying any filler compounds, because moisture they warn, will then not have a chance to disrupt the created sacred bond between the epoxy and the filler because it they feel is chemically bonded. Well to that, remember that by the time the filler is added over the epoxy the quality of this sacred "biting" or "Becoming one with the Epoxy" or chemical bond available via the filler into the epoxy is minimal at the very best and more likely truly in parlance and certainly no better than that of a properly prepared 35 grit to metal foundation mechanical bond setup.
If water was and is of an actual concern in this given rebuttal. i.e. - In extending metal protection with moisture bonding barrier issues, then one should be using something designed just for that a dedicated Epoxy system admixture specifically compounded and used for hydrophilic water conditions, which by the way is a whole different kind of Epoxy system or ball game altogether.
So the take home message here in service to our humble needs under the shade of our aging shade tree shops, is to have a doable workable understanding of a little polymer chemistry. That way, one can then rest assured either application ways as explained above are O.K. for all of our little automotive practical purposes, needs and concerns.
rustover - Long Winded Version 1.0 ..
There is nothing really wrong with the old tried and true way of 36 grit biting into clean raw clean metal, ( Mechanical Bond ) thereby trenching a foundation foot hold for the primer. Remember when using a true Pure Epoxy Admixture which consists of a very high quality resin / amine ratio coupled to a low solvent concentration blend mix level with no talc spores for sandability, and resulting in a final admixture requiring no induction times, which truly exotherms, ( heat generated from chemical bonding actions ) ; The ability to obtain a true Chemical Bond when using two different chemical yet compatible commodity compounds ( ie. epoxy to filler ) , then Yes the matter of spraying the epoxy first onto the virgin substrate prep'ed metal then applying the filler before the epoxy completely kicks ( exotherms ) to get a true full chemically bonded adhesion is obtainable. Because one is enhancing and achieving an overall bond known as a pure" Chemical Bond" and not just a pure " Mechanical Bond " . Now with that said, using a "compounded" Epoxy admixture system ( Sandable Epoxy Primers with varying high solvents ratios with various micros talc concentrations for sandablitly ) this truly achievable Chemical Bond quality decreases in real time linearly in relationship to the varying degrees of these compounded epoxy ratios used.
In other words, getting a truly chemically set rock solid effective chemical bond with these products is so-so. So in our cases, a properly executed 36 grit into metal prep would be just as similarly effective as applying filler to a 12 hour old kicked epoxy spray mechanically bonded to the metal surface that has already had it's initial active chemical exothermal actively completed.
In rebuttal to this, you will then hear folks attempting to warn and tell you, a repeatable mantra chant that dictates it is most important to Epoxy first onto the metal substrate surface ( A Mechanical Bond by the way ) before applying any filler compounds, because moisture they warn, will then not have a chance to disrupt the created sacred bond between the epoxy and the filler because it they feel is chemically bonded. Well to that, remember that by the time the filler is added over the epoxy the quality of this sacred "biting" or "Becoming one with the Epoxy" or chemical bond available via the filler into the epoxy is minimal at the very best and more likely truly in parlance and certainly no better than that of a properly prepared 35 grit to metal foundation mechanical bond setup.
If water was and is of an actual concern in this given rebuttal. i.e. - In extending metal protection with moisture bonding barrier issues, then one should be using something designed just for that a dedicated Epoxy system admixture specifically compounded and used for hydrophilic water conditions, which by the way is a whole different kind of Epoxy system or ball game altogether.
So the take home message here in service to our humble needs under the shade of our aging shade tree shops, is to have a doable workable understanding of a little polymer chemistry. That way, one can then rest assured either application ways as explained above are O.K. for all of our little automotive practical purposes, needs and concerns.