Suspending Chrome oxide polishing powder

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SUMMARY

This discussion focuses on the effective mixing of 0.5 micron chrome oxide polishing powder for application on leather or balsawood substrates. The user, Mike, initially attempted to mix the powder with mineral spirits but faced issues with clumping, which rendered the mixture ineffective. Expert advice clarified that chrome oxide should remain in a suspension, not dissolved, and recommended using thin cutting oil, specifically 5W motor oil, for optimal results. Additionally, the discussion highlighted the importance of using finer grit materials, such as 5000 grit silicon carbide sandpaper, prior to applying chrome oxide for achieving a polished finish.

PREREQUISITES
  • Understanding of colloidal suspensions and emulsions
  • Familiarity with chrome oxide powder and its applications
  • Knowledge of grit measurements and their significance in polishing
  • Experience with mixing techniques for abrasive powders
NEXT STEPS
  • Research the properties and applications of chrome oxide powder in polishing
  • Learn about creating effective suspensions for abrasive materials
  • Explore the use of 5W motor oil as a cutting oil for polishing applications
  • Investigate the differences between various grit sizes and their impact on surface finishing
USEFUL FOR

This discussion is beneficial for hobbyists and professionals involved in woodworking, metal polishing, or any craft requiring fine surface finishing techniques. It is particularly relevant for those using chrome oxide powder and seeking effective mixing methods for optimal results.

Mike shults
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Hi,
In new to this forum, but I need help on mixing .5 micron chrome oxide powder. Into a liquid so I can put it into a mini spray bottle to apply to a leather or balsawood substrate for polishing steel. I was reading online about examples of different things being mixed together for example like salt and water, and the salt is soluble in the water. So what does this mean? If the salt is soluble In water. Does that mean that is an emulsion, or does that mean the salt is now ineffective in the water now? Also i was wandering what miscible means also?

Anyways back to the chrome oxide powder. I did try to mix 1/8 tsp. of powder into a 0.5 ounce spray bottle, with mineral spirits and put 3 small bb shot pellets to help mix when I shook the mixture. I don't want the mixture to spray out in clumps, because its a very fine abrasive, its .5 microns, and I figured if it came out in clumps it would be ineffective. This didn't work. It would not mix. I thought about using glycerin and denatured alcohol. If the D alcohol dissolves the glycerin will the glycerin be ineffective if it desolves? I just figured that a half and half mixture would help the mixture stick to the substrate better, because I tried straight denatured alcohol, and when it evaporates the powder doesn't stick to the substrate. So will glycerin and denatured alcohol mix together? Any suggestions?
Thanks,
Mike
 
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You can think of Chromium oxide as little crystals, like the talc in body powder. In order for the chrome oxide to do its job it needs to remain solid, because each grain has to be able to scratch the surface - that is what the process is. The result appears shiny, but under high magnification you can see the abrasion marks.

Some definitions
mixture - like salt dissolved in water - the salt crystals no longer exist. Not this one. You want your "crystals" to be in there working, not gone completely.
suspension - like a mud puddle after you stir it up. This is okay as long as the liquid does not harm the surface you are working.
emulsion - like mayonnaise. Again not what you want.

You want: thin cutting oil. A suspension. I use chrome oxide powder on a glass plate with 5W (US viscosity grade) motor oil to sharpen my wood chisels. You should also consider 5000 grit silicon carbide sandpaper to get most of the final buff going. Chromium oxide, because it is so very fine, does not effect rougher surfaces quickly. 5000 grit first, then Chromium oxide. You can also use "rouge" buffing for surface shine: Jewelry and some knives often go the Black(emery)->Brown(tripoli)->White route(blizzard) route to a nice shiny result, mostly on a buffing wheel. Chromium oxide is used mostly for final sharpening, especially harder steel like stainless steel knife blades.
AFAIK.

In the US, commercial green powder is typically sold as 8000 grit. Grit = particles per inch. So it is close to the spec you gave in microns. I think.
 
Last edited:
0.5 microns is approx 60,000 grit. 60,000 grit chrome oxide paste is available lots of places (if you're interested).
 

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