Applying the bluing correctly is somewhat different than you may be used to, but it absolutely works!
After thoroughly degreasing; deciding whether to repair, or restore the finish and fixing the texture to meet your expectations; it is best if you pour a little bluing into a cup or small plastic container so you don't accidentally contaminate the bluing in the bottle. This next point is CRITICAL!
Do NOT use cotton balls, or Q-tips to apply the bluing. Do NOT use paper towels either. (Cloth is also bad, but cotton swabs are the worst!) The problem is: contamination from the applicator messes up the bluing. Let's start with the smallest problem. Cloth has detergent and sizing in it from manufacture. (And no matter how often you wash it, there is always some left because you wash it in detergent!) The next worst is paper towels (or toilet paper as another company suggests). That has inks, softeners, bleach and a host of other contaminants, again, from the manufacturing process. The softer the paper, the more stuff there is in it! But for sheer destruction of the bluing process nothing matches cotton swabs. They are processed with lanolin and other softeners to keep them from drying out. They can be sterilized, but they still are loaded with grease. Even if it is sterilized, that just means it is germ free grease to screw up your bluing!
Nearly every company that sells bluing promotes the use of Q-tips, or cotton swabs as an applicator. It is no wonder that the bluing tends to streak and spot up!
THe BEST applicator for Van's Instant Gun Blue is a soft-bristle toothbrush! (There are specific times when we use steel wool, but that will be described in more detail later.) A toothbrush cannot be sold with contaminant in it since it is going into your mouth!
Dip a clean toothbrush into the bluing, and rub it into the area that needs it. In my experience at gun shows, when customers at my table do that for the first time, they act like they're dealing with nitroglycerin! Rub it in - it can't hurt the existing bluing. Every molecule of steel that is white or gray is chemically active and will absorb the bluing. Everything else repels it like water! So it only penetrates the metal where the bluing is missing and does NOT damage or overlap the existing blue.
NOW KEEP IT WET WITH THE BLUING FOR THE NEXT 5 MINUTES! Rub it in with the toothbrush, back and forth, to keep the area wet with the bluing. The longer you keep it wet, the farther it soaks in and the darker it gets. It may take more or less time to soak in to match the original blue based on the hardness and porosity of the metal. Just take your time ... you can't over do it! ThIs product cannot soak into the metal farther than the "Hot-bluing" did - so it can't get too dark! When it is dark enough, wipe it dry with a paper towel and wipe it down with a pertroleum based oil to neutralize the acid ... and you are done!
If you can't seem to get it dark enough, here are the three most common solutions.
#1 Heat up the metal to between 90 degrees and 150. Just warm to the touch. This expands the pores and allows deeper penetration, and darker color. Rub in some fresh bluing while the metal is warm. Do not overheat. If the bluing drys or sizzles when you apply it, it is too hot. This product is only working while it is wet!
#2 If the texture is slightly rougher than the surrounding territory, it will not only look slightly duller, but slightly grayer as well. This is because the microscopic ridges in the rougher metal reflect light back toward you, while the smoother areas bounce it away from your eye. To achieve a perfect match, the texture must be perfect as well. (review the chapter on texture)
#3 Sometimes the bluing does not get dark enough, because the metal isn't clean enough. Clean with a different degreaser and then re-blue. (review the chapter on degreasing)
It might be helpful if you checked the metal with a magnet. First check the barrel (that is always good steel) and then the receiver or trigger strap. If the magnet doesn't grab the metal as strongly on the receiver as it did on the barrel, it is probably an alloy and will take some tricks to get dark enough. (see above) This bluing reacts EXCLUSIVELY to ferrous metals. If it can RUST - it can be blued! This product will NOT work on stainless steel, or aluminum, or on "pot-metal" but it WILL work on everything from cast-iron, to carbide steel.
Always neutralize with a "petroleum based oil" right after bluing. Petroleum based oils range from transmission fluid, to gun oil, to sewing machine oil, and hundreds of others. DO NOT try to neutralize with a "synthetic" product like "Rig", "WD-40" silicone or teflons, etc. They are neutral and the bluing is acidic. You kill off acid with alkali and all oils are mildly alkaline. Wiping it down with anything else just buries the acid rather than killing it off.
Do not let the bluing dry. Always WIPE it dry. There is always some precipitation of bluing salts that leaves a gray film on the newly blued area. OIl removes it. But if you wait... those salts get hard (like a hard-water" mark on your sink) ... and the oil won't remove them.
Here is a scenario that may help. Let's say you fixed a small spot on the top of a barrel and when you were applying the bluing, some of it drooled down under the barrel at that point. You wipe the top of the barrel with oil and everything looks great. The next day you notice a white mark under the barrel, and it looks like the bluing has been removed. Even if you wipe it with oil, it doesn't go away. Here is what you do. Since the bluing has dissolved that salt in the bottle, it can certainly dissolve it again. (Here is where we use steel wool as I mentioned above.) Dip a piece of #0000 steel wool into the bluing (not into the bottle - steel wool has oil in it and can contaminate the bottle.) and now wash that white mark with the bluing and steel wool. The minor abrasion of the fine steel wool, and the mild acidity of the bluing, dissolves the white (bluing salts) mark. Wipe it dry with a paper towel, and oil right away. Click for advanced techniques.