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ACID ETCHING


  • From Bob

    In reply to those who want to know a bit more about my acid etching technique:      Firstly I cover the egg with  2 coats of paint,* then after drying (polymerisation to be precise) at least 24 hours, I draw my design on the surface with an indelible ink marker. I then engrave all the details  (for example the veins on leaves) with a mini drill thus exposing the surface of the egg in those places.

    Afterwards I use the drill to 'burn off' the background areas to be etched. At this stage it corresponds to the first of the 2 photos I sent last time. You can see that I used silver paint in this case.

    The next step is the acid bath. I block the blow holes at each end with wax and then place the egg in a glass jar. I then add the acid, just enough to cover the egg. The problem is that the egg tries to pop up to the surface so you have to weight it down with something heavy enough but not too hard to avoid breakage.

  • The etching time depends on :

  • The thickness of the egg shell
  • The depth of etching required
  • Above all the concentration of the acid  


  • Evidentally the stronger the acid the more rapid the reaction with  the calcium carbonate. Here in France you can buy hydrochloric acid from the drug store ( notice that I'm making an effort to use American terms!) which is 35% by volume HCL.

    In the beginning I used it without diluting.........the egg dissapears in a foam bath! It's best to dilute 50/50 with water, it's easier to control. You have to take the egg out regularly (using gloves of course) and rinse with water, wipe off the dissolved shell (scum) then check the depth of the etching. If you leave it too long your down to the membrane which can be catastrophic depending on the thickness of the remaining shell (ever done it?)

    I have and managed to get the membrane out a couple of times (goose shell membranes' are tough!!) I didn't know that you could use hypochlorite (sorry, bleach) to dissolve it.

    Once I'm satisfied with the result ( a good trick is to hold the egg up in front of a light bulb, you can get an idea of the thickness by seeing the amount of light that passes. Another way to judge is by lightly tapping on the egg and judging the sound that it makes). I rinse the egg thoroughly, then put the kettle on. This is for making tea (very important!) and also for getting that paint off the egg. I take a 'Scothbrite' ( a sponge/scouring pad) soaked in boiling water then rub the egg while it's still scalding hot ( dangerous hobby isn't it?) The paint just comes peeling off revealing the beautiful white etched egg.

    It's the moment I really love! especially after hours of hard work suddenly discovering the result is eggsciting........ At this point I either leave the egg natural just finishing with a varnish protection or I go on to the next step :      

    I paint the egg with 3 coats of paint* using either gold,silver, copper or pewter colors. For an 'old' pewter finish I start with 2 layers of silver and then 2 layers of pewter color. After drying I cover the egg with a layer of diluted black acrylic which I leave for about an hour only. I then rub off the black paint from the areas that haven't been etched. Thus highlighting them and allowing the lighter silver to show through. The end result with a bit of luck and very black hands is the egg that you have already seen.

    I think the initial artwork is important, I like it to be original and inspired from nature for example. The bore holes can be filled with a thin film of acrylic paint which after a few coats doesn't even show.

    Afterwards there's just the problem of finding a support which is in harmony with the egg and shows it off to its best. I am still working on this aspect and haven't as yet ,come up with a satisfactory solution. I like the idea of using such materials as wood (not neccessarily lathe turned) stone,slate or metal. Ideally each egg stand should be designed with repect to the egg displayed.

  • * Paint by 'Lefranc&Bourgeois'  called Deco Metallic -water based metallic acrylic.

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