We get this question all the time. Engineers read the spec sheets for one of the Vertrel^® products and see that it has a low K_b value. From this they erroneously deduce the product is a weak cleaner and unsuited for the cleaning application. In fact, when it comes to the Vertrel^® solvents, nothing could be further from the truth.

The truth is that the K_b value is not a particularly meaningful test for Vertrel^®. It's sort of asking the wrong question. Here's why:

Technically, solvency (or "cleaning horsepower") usually is measured by an industry benchmark called the Kari-Butanol test. In this lab test, a standardized test material -- a thick, rubbery, eraser-like gum -- is immersed in the solvent for a certain period of time and under certain prescribed conditions (e.g., temperatures, pressures, etc.). The lab technician then measures the remaining gum to determine the quantity of material that was dissolved by the solvent. Simple, fast and easy.

The result of the test is an index called the Kari-Butanol value. This is usually reported on product spec sheets as a K_b value. A higher K_b value is better and means the cleaner is more aggressive or active. Mild cleaners have low scores in the tens and twenties; powerful cleaners like the old chlorinated solvents have ratings in the low hundreds.

Now, most of the Vertrel^® solvents have K_b values in the mid-30s, which is similar to the old Freon products and which should mean they are mild. But this is not the whole story.

The Kari-Butanol test is an old test and is well-suited to old-style industrial cleaners. In the old days, using a K_b value to compare the old industrial cleaners like methylene chloride, perc, TCA and trike made sense because of the types of parts which were being cleaned (big) and the types of contamination they were trying to remove (gross). There also was another trade-off from these strong solvents -- they often had compatibility problems with plastics and other components.

But today's world is different. None of those old-style solvents are used today in any precision cleaning application. Even more importantly, nobody's trying to remove heavy, rubbery gunk -- at least, not from a medical device, the Space Shuttle or some ultra-small BGA chip. So the K_b test is very much obsolete. The answer doesn't make sense because the question is wrong.

In the place of the Kari-Butanol test most engineers are substituting systematic testing procedures, rigorously testing solvents on their components, their contamination and their cleaning processes. This makes sense because it's a test of real-world conditions. Often, the results are unexpected: Vertrel^® solvents clean as well as or even better than cleaners with much higher K_b values. Informally, we call these surprising results operational K_b values.

In these real-world cleaning of oils and fluxes, the Vertrel^® solvents clean much more effectively than the Kari-Butanol test would suggest while maintaining excellent materials compatibility. In fact, it's pretty amazing: Vertrel^® simply whisks away oils, grease, fluxes, and a whole host of different organic contamination. Vertrel^® CHD, for example, removes oils as thoroughly as methylene chloride, with none of the toxicity problems associated with that old-style cleaner.

So don't be concerned if your favorite Vertrel^® solvent has a low K_bvalue. We've tested the cleaners and they work great. Give them a try. For precision cleaning applications, Vertrel^® specialty fluids are your best choice.

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