Our work bench is stocked with a MENDA dispenser full of "pure" (not denatured) 190 proof Ethyl Alcohol (Ethanol). We use Ethanol for a variety of cleaning jobs, including as our favorite solder flux remover since the banning of our old favorite 1,1,1 Trichloroethane. We buy our Ethanol as Pure Grain Alcohol (PGA) from area liquor stores in an adjacent "wet" county, usually in the Everclear brand available as 190 proof (95%) alcohol (the less common 151 proof (75.5%) alcohol variant should probably be avoided as a cleaning agent). It is possible to obtain 200 proof (100%) Ethanol (also called anhydrous or water-free), and it is possible to avoid most of the stiff tax on drinking alcohol ($13.50 federal excise tax per  proof gallon equivalent), but the 200 proof material is not really superior to the 190 proof in this application, and we use such small quantities that avoiding the admittedly hefty tax is not worth the hassle. Distillation can concentrate Ethanol to 95.6%; the mixture of 95.6% ethanol and 4.4% water is an azeotrope which cannot be further separated by distillation. Hence, 190 proof (95%) Ethanol in water is common since the 200 proof material requires extraordinary measures to produce. After working with Ethyl Alcohol as a cleaner, you may have second thoughts about ever drinking the stuff again.|
Home | Tech & Tips | Service Tips |
We no longer use or recommend Completely Denatured Alcohol (CDA) for electronics applications. Denatured Ethanol has various denaturing agents added to render it unfit to drink (our beneficent government is apparently willing to blind winos to protect the tax revenue stream). There are also many types of Specially Denatured Alcohol (SDA), a few of which may be suitable for electronics use (reagent alcohol is a possible example), but SDA is not readily available to the general public, and further discussion is beyond the scope of this effort. CDA is the stuff sold in paint stores and the "big box" retailers as denatured alcohol. Among other things it will always contain gasoline or kerosene in the United States, and may be based on Ethanol running as low as 160 proof (80%). Formula Number 19 is the most common variant of CDA available in the US; see our US Formulas for Completely Denatured Ethyl Alcohol / Ethanol page for details (formulas vary in other countries). The denaturing additives in CDA render it more aggressive than straight Ethanol; CDA can damage some plastics like ABS.
Isopropyl Alcohol (IPA), commonly called "rubbing alcohol", is a considerably less efficient cleaner and it makes your shop smell like a doctor's office. Commonly available rubbing alcohol is usually 70% Isopropyl Alcohol with the balance as water, but 91% Isopropyl Alcohol is available from some retailers. Anhydrous or 100% Isopropyl Alcohol is available and is sometimes used as a flux cleaner. Occasionally, a stubborn stain will yield to one of the alcohols when all other cleaning agents fail, but ordinarily they are mediocre performers. Both Ethanol and Isopropyl Alcohol are generally safe on plastics, but as noted above, denatured alcohol can cause problems.
A chlorinated type solvent is useful for some tasks, including the removal of particularly stubborn solder flux residue, and oils and greases in general. In January of 1996, our government, in its infinite wisdom, outlawed the best of the bunch, 1,1,1 Trichloroethane a/k/a methyl chloroform (and the Freon cleaners) as ozone depletors. 1,1,1 was legendary among technicians as good and safe stuff; despite many unfounded accusations, it was never implicated as a carcinogen. The current replacements for 1,1,1 are not so great; many are suspected carcinogens. At present, the best reasonably priced replacement for 1,1,1 is tetrachloroethylene a/k/a perchloroethylene. "Perc" is ordinary dry cleaning fluid. Perc is found in some formulations of chlorinated non-flammable "brake cleaner" available at any auto parts outlet and elsewhere. Avoid the non-chlorinated brake cleaners; they contain particularly nasty solvents like toluene and xylene and are flammable. Also avoid any formulation containing dichloromethane a/ka methylene chloride (the old standard paint stripper); it is too "hot" for electronics applications. Trichloroethylene is actually our present favorite, but it is hard to find. Buy brake cleaners or electrical cleaners that contain only Tetrachloroethylene or Trichloroethylene or mixtures of the two. Bear in mind that these chlorinated cleaners will damage many plastics, especially ABS and similar materials. Good ventilation is especially important when working with these chlorinated solvents.
Our work bench is also equipped with a MENDA dispenser full of garden variety mineral spirits. Buy the low odor or deodorized kind; the really cheap stuff does smell stronger. Mineral spirits is useful for degreasing and is generally safe for short term use on most plastics. Real Turpentine is more aggressive than mineral spirits, smells stronger, and is more expensive.
Castrol Super Clean is the best "Fantastik" class cleaner we have found. It will clean the skin right off your hands if you are not careful with it (wear rubber gloves)! It is unsurpassed at removing old recorder ink deposits and similar stains. It will often clean too well, removing the paint from panel label engravings. It is an essential weapon in our cleaning arsenal. All Fantastik type cleaners are corrosive to aluminum if contact is prolonged and some painted surfaces may also be sensitive.
Polishing compound of the type used in the manufacture of plastic eyeglass lenses is invaluable for restoring meter face plates, plastic lenses, and plastic covers of all kinds. Bad scratches can be removed by wet sanding with progressively finer sandpaper (the final sanding should be with 1200 or 1500 grit), followed by the polishing compound. A minute or two of manual rubbing with a soft cloth or even a paper towel, dampened with a few drops of the polishing compound, does the trick. The sanding can often be omitted in the case of superficial scratches with still quite spectacular results. Once this technique is mastered, you can truly work miracles with any clear or shiny plastic surface; even painted surfaces respond under some circumstances. One exception to the use of this technique is if the clear plastic surface has been chemically treated, as with the scratch resistant coating often applied to plastic eyeglass lenses, but this is not commonly seen on acrylic meter face plates.
Automotive paint masking paper makes an excellent work bench cover for dirty jobs. It is cheap, surprisingly resistant to liquids, and can be disposed of after each use. The twelve inch width works best for us, but it is available in many other widths. The 3M brand material seems to be the best. The plastic coated version causes more problems than it solves.
NOTES: It is recommended that rubber gloves and eye protection be worn whenever working with strong cleaners or solvents. Good ventilation is essential when working with most solvents.
FTC Disclosure: Neither AnaLog Services, Inc. nor the author has an economic interest in any of the companies or products discussed above, and no monetary compensation was received. Free samples were received from various manufacturers. None of the manufacturers / distributors was aware this page would be written.