All,

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!

Derrell

Derrell says,

I've posted a couple of photos of a diesel shell that I recently

subjected to air honing with Aluminum Oxide.
<SNIP>
> 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!

Actually, there are 2 good reasons not to use Al Oxide. Both have
already been mentioned. The first is that it is a significant
inhalation hazard. I find the idea of using a cardboard box to contain
it SCARY! When I used it in my grit blaster there was always some small
leakage and that's a much tighter box. If you use Al Oxide, use a well
fitted particulate filter mask as well. The second reason is disposal.
About the only place Al Oxide can go is to the landfill. In some places
it is not legal to put it in the regular trash. If you've got acid soil
in your yard you can actually kill 2 birds with one stone by spreading
used baking soda on it! That said, I agree, baking soda often does not
"cut it" as well as Al Oxide, but please be safe!

Regards
Bruce Smith
Auburn, AL

Bruce makes very valid points.

Just to clarify, I began using Baking Soda years ago simply to "Hone" the surface of both styrene and resin kits to provide a little tooth before they are painted. It also smoothes out minor accidents with "Testors" so that they disappear when the model is painted. I like it because it is easy, convenient, cheap, safe, and effective. I don't use it to remove paint although it may work for that and don't claim it would be an effective heavy duty honing media.

On my trip this morning to the hobby shop i bought the Feb. issue of RMC and look forward to reading Jack's article on building a "Media Cabinet" so I can do it inside in case it get really cold in Florida.

Bill Welch

Thanks Bruce. All,

Never too much safety warning. As Bruce said the inhalation hazard has already been mentioned - I guess I got a little lax about the "California" note because I expect my peers to have the same common sense that I have. Plus every AlumOx container I've seen has a Caution or Warning label on it - and if someone can't read that they probably are not reading this!

For the record I always use a good particle mask. Always.

As to the cardboard box; actually there were a couple of them. The first was simply an open top box that I always used outside with the Badger 260 (which is a pain in the butt because it isn't always that prolific to begin with - grrrr!). I always used a mask and gloves. It's purpose was to block the occasional breeze and to perhaps capture some of the AlumOx - I'll admit that was not a good practice but since I only occasionally air honed anything at the time (perhaps 2 - 3 times a year???) it never seemed to be a big issue and didn't warrant buying a cabinet. The second box had been similarly modified as Jack's box. Again! I never used it in an enclosed space and I always used a particle mask. I never used anything more in it than the 260. Neither of these are serious suggestions nor did I expect anyone to really take that as such (guess I trust folks intelligence more than I should). I don't advocate cardboard, not only because it does get a bit leaky after a while, but also because it is at best a temporary device for all the effort put into it.

As to disposal – guess that is just part of the process. Not everything can be handed to you and some things take work to get the best result. Just another one of the "sacrifices" our society is rapidly forgetting.

Look. Don't do anything I suggest if it scares you or you can't figure out how to overcome the obstacles. I enjoy sharing what I have learned of my own volition and I hope some of you find it helpful in your modeling efforts.

Enjoy!

Derrell

I haven't seen it so much on this group (since I haven't been here very long) but on others there has been a lot of noise about air honing plastics with hard grit materials such as AlumOx. Aside from the safety issues, the general consensus has come across that it will destroy the plastic. Perhaps everyone here already knows better. Still my primary point hasn't been about the safety issues. As I said, that is a matter of common sense - it is what it is and there are steps to overcoming that. My point is to share with you that I've found the fear of hard grits destroying the plastic to be a myth. Like so many myths, it is passed along over and over again because no one challenges it. There are a lot of these myths in this hobby.

If you like the baking soda by all means use it. Nothing wrong with a personal choice. But if you feel frustrated with it as I did you now have knowledge that someone finally challenged the fear of hard grit on plastic (and it didn't cost you even a junk model). Now you can see for yourself with less apprehension. That is all I've hoped for.

Derrell

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!

Derrell

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