We have found over the years that there is a lot of mystery surrounding these two admonitions regarding the use of this kind of product.
When the SPI "Two-in-One" Easy Duster™ can is stationary, the liquid propellant (which in this case is also the product itself), fills on the order of 90% of the can's volume, with the head space being filled with nearly 100% vapor of the propellant. In other words, this is the classic system whereby the liquid vapor is in equilibrium with the liquid. The headspace is pure vapor with no droplets.
Also, although the product starts out from the manufacturers, for example, DuPont, with very high purity, and the impurity level is in the low ppm range, there are a number of ways that impurity levels can be increased, and in some cases appreciably, by the time the product gets to the point where it is ready to be used. For example, some fillers of these kinds of cans use the same lines that are at times used for other products such as hair sprays and other aerosol products. And while the lines are purged of the previous production, the point is the lines never really get completely cleaned out. Hence there is the very real possibility for residues from other products to end up in a duster can. In order to eliminate this source of contamination, we certify that all SPI "Two-In-One" Easy Dusters are filled on lines that are 100% dedicated to the filling of this particular product, namely R-143a.
But there are other sources of product contamination, for example from the "o" rings in the filling lines and also, and this is the little secret that very few users concerned about cleanliness know and understand, is that there is contamination from "o" rings that are in the can itself as part of its construction! Yes, while most have not ever thought about it, one or two "o" rings are actually a part of the construction of the can and in fact are absolutely necessary to contain the product and reduce any leak rate to essentially zero levels. And these "o" do require a plasticizer for them to maintain their properties with time. And the "older" the particular duster can, one could expect that there would be more and more leaching of the plasticizer into the product.
Now this might sound pretty horrible, and indeed if first perceptions were correct, it would be horrible. But it is not horrible! Indeed, and this is the point of this entire page, if the product is used as directed, there could be ten times more plasticizer in the product and it would still not matter!
The explanation is very simple: Remember, the product itself is contained in a can with a head space, filled with vapor of the product. But the plasticizer has a very low vapor pressure and none ends up under equilibrium conditions in the vapor. And if the can is not shaken, and if the can is not tilted when used, there will in fact be expelled about as pure of a vapor flow as one could ever want to have. The concentration of the plasticizer in the product just does not matter, but that is provided the use instructions are followed exact, that is, no shaking and no tilting.
But what happens if there is shaking? Well, the shaking cases the formation of aerosol droplets in the vapor space and then what is being expelled is not only vapor, but also being expelled are small microdroplets of the product. But these microdroplets themselves contain some concentration of the plasticizer contaminating species. And these organics will indeed spread out on the surface being cleaned. And a thin organic film will result, something quite undesirable for most applications and something to be avoided.
And what about the no tilting of the can? Well, if the can is tilted very far, one can very easily get a decanting of the liquid product and with it also, the contaminating organics.
So we are hoping that this background story as to the real reasons why one must follow the rules of "no shaking, no tilting" rigorously.
As a final comment, we don't want to make it sound like we are not sensitive to the need for pure materials in the SPI "Two-In-One" Easy Duster. We can assure you we care very much. Because of our high volume and rapid stock turnover, the cans shipped from our stock are quite fresh. And that is the real reason why we go to our own select filler, we have complete control over the cleanliness of the product coming into the cans, we have complete control over the quality of the can's construction and also the cleanliness of the cans during the filling operation. And we are not ourselves purchasing some other brand of duster that has been sitting for some indeterminable period of time in some distributor's warehouse somewhere. This is all to help ensure that even though we don't think it is important if the can is used properly, we still want to do all possible to make sure that any contaminants that are present are certainly going to be at the lowest possible levels.
As a final comment, we would address the issue of "fill size", that is, how many oz. or grams of product are going into a can. There is a nasty little game going on in the industry of "duster" products and that is to keep reducing the size of a fill. It is the "duster equivalent" of the shrinking candy bar of year past. The cans being used for this particular product are an industry standard can and are rated to take 11 oz. And that is the size of the fill of the SPI "Two-In-One" Easy Duster. But if you look around at the duster cans being offered by others, you will see some that are only 10 oz, some are 9 oz, and some are even 8 oz.
So while we encourage price comparing, just keep in mind that all duster products are not created equal. It is pretty obvious, that if more ounces are in a can, the cost to fill that can and make the product overall, on a per oz basis is going to be less. And we are confident that when price comparisons are done on a price / oz. basis, you will be very satisfied that you are getting the product for an attractive price.
But we would add one more caveat at this point. The leach rates from the "o" rings will be at the same rate no matter whether the fill is 8 oz or 11 oz. But the concentration of the organics in the larger size fill will be lower than in the smaller size fills. So in addition to the economic arguments for the larger size fills, there are good sound technical reasons what the product will, at least in this one way, be "better" than if sold in cans with smaller size fills.
We just don't want our customers to be fooled by the shrinking candy bar.
