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Dark Spot On Forehead

Discussion in 'Skulls and Skeletons' started by Randy Curtis, Nov 10, 2021.

  1. Randy Curtis

    Randy Curtis New Member

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    For many years I contracted out skull cleaning. I did a few over the years but not many. Lately I have received poor results from the contractor. Therefore I started doing my own. I macerated the skulls. I have had very good looking skulls after they dried for about 2 weeks using maceration and hand cleaning in areas that needed a bit of cleaning. I have about 20 skulls using maceration and they all look nice. I use a strong peroxide to whiten the skull. I then let them dry out for about 2 weeks. I then sprayed 2 of the skulls with semi spray gloss lacquer. The first 2 I did looked very nice but after about 20 minutes the forehead on one bear and one mule deer developed a slightly darker area on the forehead about 2" in diameter? I have not sprayed lacquer on the rest of the skull but they do look very nice and white. I wonder if I used to heavy of coat with lacquer? The spot on the 2 skulls is about 2 to 3 inches in diameter and only on the forehead? All the other parts of the skulls looked very nice. In the past I have seen this before? Puzzled? Any ideas??? Thanks Randy
     
  2. Sea Wolf

    Sea Wolf Well-Known Member

    Photos? Do you degrease them? Might be possible that, if there was grease there, the lacquer brought it to the surface. Might also be where the spray hit first and there is a thicker layer of it there. But I would think it would be uncolored and not show. If you rub down that area with a rag with acetone (don't remember if it is acetone or alcohol that takes down lacquer) does it get any lighter?
     

  3. steve torna

    steve torna New Member

    Hello from Montana,
    I agree with Sea Wolf. Even though bacteria from maceration remove much of the fatty grease from the bone, maceration will not completely degrease the skull. The area that is discolored is amongst the thickest and most dense bone on a mammal skull. Other potential problems areas include the mandible and base of the skull. You must degrease them after maceration and prior to bleaching.
    Additionally, I would reconsider lacquer spray; degrease and bleach is all that is required. Natural bone is beautiful and appealing. Once sprayed, it is no longer natural; the bone loses it's integrity (quality that we are trying to present and preserve). If you feel strongly about sealing then consider a water soluble sealer such as floor wax, but use a flat or satin version, nothing heavy or glossy. Floor wax can be diluted with water to achieve a barely noticeable result. Most of my skull collection consists of completely natural bone specimens but because a significant portion are handled and used for teaching and study, I do apply a dilute solution of Johnson and Johnson floor wax; I simply paint it on with a brush. If the wax is applied sparingly, the bone will retain a natural look and feel.
     
  4. Randy Curtis

    Randy Curtis New Member

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    Thanks for the info. I am still learning and want to get the best result I can. You and sea wolf have helped me a lot. For man years most of my clients chose to do shoulder mounts. Now they prefer nice, clean skulls. I just finished degreasing today and looking for the right sealer. I never considered the natural look without a sealer? I will think about it. Is Johnson and Johnson a liquid or a wax? I assume it is a liquid? I have always thought it was a wax? How do you apply it?? Thanks for the info.
     
  5. steve torna

    steve torna New Member

    Hi Randy,
    Johnson and Johnson floor wax is a liquid. I simply paint it on with a brush. You may dilute it or apply full strength. Use a "practice" skull to test before application; make sure you like it. I think that you should not coat them and leave them completely natural. Make sure that the delicate nasal bones are painstakingly preserved because the presence of the nasal bones not only separates professional from amateur work but the essence and beauty of the skull are found in those details. I am always horrified when I see an otherwise magnificent skull with the nasals torn out; it ruins the skull.
     
  6. Sea Wolf

    Sea Wolf Well-Known Member

    After using different things over the years for a sealer, I now use a resin that the museums use. Called Paraloid B72 it dissolves in either acetone or alcohol. I keep a solution of it in a bucket and submerge the skulls in it, let them drip off and then hang them to dry. One advantage to this stuff is you can make it as thick or thin as you like. The skull will be sealed and protected from dirty hands when someone is looking at it. Dirty areas can be washed off with soap and water with no harm to the bone surface. Another bonus of this is that you can save overboiled and chemically damaged skulls that are turning to powder and falling apart. This stuff will soak into the bone and stabilize it, stopping any further degradation. There is no waste with it as any drips are returned to the container to dissolve again. If an area of bone seems to have a shine to it, the surface is easily rubbed down with a clean rag and some acetone. Due to the expense initially, it would not be something to use with a one off skull but, if you are going to do a number of specimens it is great stuff. Another use is to brush some on an area of bone you are going to write on, let it dry and then write on top of the resin layer so the bone is protected. I use India Ink and, when that is dry, seal over the top of that with another layer of resin.