Re: Air Honing plastic

Richard Hendrickson

On Jan 28, 2012, at 9:14 PM, derrell wrote:

I've posted a couple of photos of a diesel shell that I recently
subjected to air honing with Aluminum Oxide. Pressure was between
80 and 140lbs (the max of my compressor). Look in the Photos
section for "Air Honing Plastic". I hope for those who are
interested that this is more of encouragement rather than proof of
a point.

But why bother with this at all? I found it expedient in this case
because I needed to strip the old paint from several cheap ebay
locos needed for a promotional project. We want to put the company
colors onto clean shells. The models will be sent to some of the
magazines for review of a particular product. Naturally we want to
put a good foot forward. Stripping the shells (there are four of
them) with the Pinesol worked very well but they were still not
clean enough. The air honing did the trick.

I think if you are inclined to study the photos it will become
clear that this treatment is very successful. The detail really
shows no degradation from the high velocity particles and I don't
think it really matters if it is one cutting material or another.
Would baking soda work just as well? Sure. But this is
substantially faster. Substantially! If you already have a blasting
cabinet there isn't any reason not to use it. If you don't I'd
encourage you to get one because they are quite useful. Or make
one. I like Jack's idea. I've used a cardboard box!

I'll strongly second Derrell on this. Many years ago, I made my own
grit blasting booth from scrap plywood. It has interior lights and a
hinged plexiglas front so I can see what I'm doing and, as with the
booth Jack Burgess made, access for my hands is through sleeves with
elastic cuffs cut off from a cheap nylon shell jacket. I wrote a
brief article about it in, IIRC, an antique issue of Model
Railroading. I use it all the time; in my book, it's as much an
essential tool as a paint spray booth and air brush. No serious
modeler should be without either of them. Mine is in my garage where
I can hook it up in seconds to the big compressor I also use to fill
car and wheelbarrow tires, air mattresses, etc. The plexiglas front
gets cloudy after awhile (mostly just dusty), but I clean it up with
plastic polish periodically and it still works fine. Fine aluminum
oxide powder works much faster than baking soda and, as Derrel says,
it absolutely won't damage the details on injection molded plastic or
molded resin. Bruce Smith's cautions about aluminum oxide are worth
noting, and using a respirator is certainly a good idea, but no dust
gets out of my booth because of the elastic cuffs and the rubber
weatherstripping around the hinged plexiglas front; the only grit
that escapes is what remains on my hands and on the parts I'm grit
blasting. I routinely grit blast trucks, leaving a surface with
enough tooth to hold paint or, in many cases, to resemble dirty
trucks so well that they don't need to be painted at all. I also
grit blast completed resin or unpainted styrene models and then wash
them in soap and water to remove any grit residue, after which the
paint that goes on them is really there to stay.

Richard Hendrickson

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