Vacuum: Good in Space and Here on Earth
I have written many times on the care and feeding of meteorites. I want to visit that terrain again this month. I saw a commercial on TV for the Reynolds Handi-Vac and thought that sounds like a great idea for keeping moisture away from bagged meteorites. Well, I have spent a short time with the machine and will tell you what I have learned thus far.
I guess some basic information is in order. First, as we all know iron rusts. But, three items are necessary for rusting to occur. They are like the triad for fire remove one and combustion stops. For rusting you need of course the iron, also oxygen, and moisture. Well we can do nothing about the iron it is what we want to keep and protect. But, the oxygen and the moisture we can control. This is where vacuuming comes in. Remove the air and the moisture contained in the air and stop rusting completely. Maybe. There is no guarantee that some other type of corrosion could not continue to eat up a contaminated meteorite. But, a vacuum is what they were in out in space and returning them to that environment can not hurt.
This is not a new idea for me. I have vacuumed meteorite containers in the past. Put a refrigeration valve on the side of an ammo box and you can either pull a vacuum or push in dry nitrogen. I have done both. But it is inconvenient and requires a vacuum pump and compressor. Both of which can be made using an old refrigerator compressor if you don't have a regular one of each. But, it is still not simple. And you lose the nitrogen or vacuum each time the box is opened. So vacuuming works best for meteorites that will almost never be looked at. Not what I needed for specimens I was cutting to sell and keep nice until ordered.
The Handi-Vac however, is small, portable, and simple to use. The bags can be opened and resealed repeatedly. Something not recommended in its primary application for food storage. In a few seconds the bags are evacuated and pulled tight around the specimens. Here is the first caution. The bags are easily punctured by sharp edges and corners on meteorites. So wrapping the meteorites or stacking and wrapping slices in a folded paper towel provides all the protection from puncture needed.
An additional benefit of the vacuum bagging is that the specimens are motionless in the bags . There is a reduced chance of damage from banging around during handling.
Now I want to make it perfectly clear as one of our former presidents used to say, that tremendous pressures can be applied to objects by vacuuming. You need to be careful about what meteorites you choose to use this process on. Very friable meteorites are out; without using some kind of pressure resistant container surrounding them. And random packing of slices with fragments could result in them squeezing each other until some are broken. Neat stacking is needed so that the pressure is uniform on the wrapped package.
I found that it was necessary to run the machine long enough for the tightest package it could make. By design the vacuumed bags are to be put in the freezer for storage and we are not doing that. Frozen food will maintain its vacuumed shape and therefore its sealed state. But outside the freezer my meteorite packages have occasionally lost their vacuum. They became loose like a regular plastic bag after a short time. I learned that if you do not pull a hard enough vacuum on the bag this will happen. But when really pulled down they stay sealed. External air pressure seems to be important in pushing on the zip closing surfaces to seal them.
What I have been doing is sealing the slices and windowed individuals in the vacuum bags then putting several bags into another regular zip bag with some desiccant. So even if the vacuumed bags lose their seal they began dry and are in a dry environment still so no rusting should occur.
We have never had much trouble with slices rusting before we sell them. However, we do have one meteorite that needs to be kept dry or little spots appear on the surface of a slice now and then. I have been using 99% alcohol for all the lapping on it and polishing the slices to reduce their surface area. This usually will solve the problem. With the addition of vacuum sealing I am confident that we have seen the last of those occasional spots of rust.
The Handi-Vac is not expensive and is very easy to use. Unlike most toys these days it even came with batteries included and a few bags to try it out on. And it was not hard to find, it was stocked in grocery stores.
Now for Something Completely Different
The Tucson Gem Show is getting close and I will be making my shopping list up. I have not gotten any of the recent falls of the past year so I will have my eye out for them. But, I really havenít much else in mind right now. Really attractive fresh NWAs often seem to make it home with me. I am still not very concerned about whether all my meteorites are classified. There is plenty of time in the future for that. I am having fun at the present just looking at their form, fusion crust and other characteristics. Later I can figure out how to get them classified if they seem special. I will probably never get the OCs classified and some I just hate to cut since they are nice whole specimens.