I have been through the archives and can't seem to find the answer I seek. I have bleached several skull 3 boar, bear, fox, otter and deer and had no problems until this bobcat. The top of the skull where the brain would be it has a dull brown color to it. I have used both 3% and 40% peroxide and had great results til now. I have varied the strenghts but still, no better. This is for my personal collection so I'm not too worried but would like my customers to came in and see a nice white skull. Any suggestions.
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My money is on insufficient degreasing. The brain is high in fat. Im guessing you had the skull inverted for a while at some point and it became overly saturated with oils. Dont underestimate the length of time allowed for degreasing. Sure some things can be done in a week - others may take a month or more.
That discolouration is almost certainly residual oils. Degrease it longer.
But what does inverted the skull mean?
I did degrease but for about only a week, and did make sure the skull was inverted so that there would be no air pockets. Guess I will degrease some more, thanks.
which degreaser or method do you find works best?
Its in the archives - including arguments Ive had repeatedly with George over this issue...
a non pterol based solvent (despite what George THINKS... solvents are NOT all equal). Go with a ketone solvent like acetone and degrease for a good long time. Take all associated safety precautions when using this volatile product. Isopropyl (rubbing) alcohol is another ketone solvent but I find it doesnt work as well. When you are through using this for a deep cleaning, switch to a surface cleaning agent like dish soap. Get the clear kind or you risk tinting your skulls purple, pink, green or any of the other funky colours they have out these days. This two tier approach I find yields optimal results for home use. There are other methods used for musueum work etc that I wont divulge here for safety reasons.
A petroleum base solvent WILL dissolve grease, but it does nothing to eliminate it. If you use a solvent in the craneal area, allow it to "soak through". This means that you've now dissolved the grease and it's free floating in your petroleum solvent. To DEGREASE the skull, NOW you should wash it in a very strong soap (Epo-Grip Bloodout/Degreaser or Eliminator from Van Dykes). This soap will the mollify the solvent and allow everything to be washed right out. Let it dry and THEN bleach the skull.
Degreasing in a petrol product followed by a surfactant is pointless - you might as well just use the surfactant intitially. Yer still only going to get a topical cleaning as now the petrol oils instead of the animal oils are deep in your bone. You've accomplished nothing. Use a ketone to get the animal fats out as ketones leave no residue of their own. No matter how many times I describe this you can never grasp it. In your attempt to disprove me once you went so far as to say put acetone, gas etc all on paper and you'll see they all leave oily residues. I challenged you then and you never responded... do your own test. Acetone will NOT leave oily residues. Its different than petrols.
What slays me about all this is that I described this before and you laughed it off... then months later someone else reposted almost exactly what I said and you nearly tripped over yourself to agree with them. If its coming from me - yer ready to dismiss it.
Isopropyl alcohol is not a ketone. Ketones have a double bond of oxygen on the carbon chain whereas alcohols have an -OH(hydroxyl) group on the carbon chain.