aek Posted October 1, 2019 Share Posted October 1, 2019 I am having trouble coating this Isotelus plaster cast. This is my first time attempting the ammonium chloride coating method. First I painted the cast with a thin layer of black acrylic (in retrospect, I probably should have used watercolor?). Then made a number of tries to coat the cast with ammonium chloride and was unsuccessful. I tried placing the cast above the smoke, below and directly in front of the flask, nothing worked. I'm wondering if humidity could be an issue? Has anybody tried applying ammonium chloride as a fine liquid spray or magnesium ribbon? Any tips appreciated. Link to comment Share on other sites More sharing options...
aek Posted October 1, 2019 Author Share Posted October 1, 2019 Link to comment Share on other sites More sharing options...
aek Posted October 1, 2019 Author Share Posted October 1, 2019 This is my set up. Link to comment Share on other sites More sharing options...
Phevo Posted October 1, 2019 Share Posted October 1, 2019 I can't say much about ammonium chloride, but I use ochre powder on my silicone casts if they lack contrast Link to comment Share on other sites More sharing options...
aek Posted October 1, 2019 Author Share Posted October 1, 2019 1 hour ago, Phevo said: I can't say much about ammonium chloride, but I use ochre powder on my silicone casts if they lack contrast Interesting, I haven't heard of ochre powder.How do you apply it? Link to comment Share on other sites More sharing options...
Phevo Posted October 2, 2019 Share Posted October 2, 2019 It's just brushed on, keep in My mind i just do it for picture purposes, if you want to display a specimen it might not be the best solution, but I can take a few pictures later to show one with and without 1 Link to comment Share on other sites More sharing options...
Johannes Posted October 2, 2019 Share Posted October 2, 2019 @aek: why did you want to coat a painted plaster cast with ammonium chloride? For photograpy you allready lost a lot of surface detail information 1.) with the plaster cast and 2.) with the prepainting so you will have no effords using ammonium chloride. Additionally you have often problems to remove the chloride completely, if surfaces of the fossil are treated with chemicals like colours or coatings or made of resin/epoxy. Some of whitening-techniques are described here (unfortunately only in german, but maybe readable with the help of online translators). Just for colouring a cast you will have better results with only using mixed acrylic colours and/or watercolour. 1 Link to comment Share on other sites More sharing options...
aek Posted October 2, 2019 Author Share Posted October 2, 2019 Thanks @Phevo I would love to see before and after pics using your technique. @Johannes Thanks for the helpful link. My idea was to experiment with ammonium chloride (and other techniques)first with plaster for photography before moving on to real specimens. The Isotelus was found only as an impression and upon making a cast of it, I noticed it had remarkable detail not visibly apparent in the mold so thought it would be fun to experiment with different effects as I can always make another cast if destroyed. Link to comment Share on other sites More sharing options...
Johannes Posted October 2, 2019 Share Posted October 2, 2019 @aek: Ok. Use of Ammonium Chloride is for taken out colouring effect from the game, so that you have no colour but pure detail. With really white plaster, you have nearly the same effect, so A.Ch. will not help you. If you want to practise, you can use fragments of other fossils directly on a "fresh split" in the meaning on the original natural rocksurface. A.Ch. dust should haft on that surfce if you follow the instructions given in the linked paper on page 72. Maybe you have to do some little adjustments in your setup (plugs/injectors/hand-bellows (sorry if I have not used the technical correct english terms)). If you try the A.Ch. later directly on the mold, you can apply different techniques (analogue or digtal) to get a "fake-positive" on pictures... Link to comment Share on other sites More sharing options...
aek Posted October 2, 2019 Author Share Posted October 2, 2019 @Johannes Great, thanks for the suggestions. I like the "fake positive " idea.. Link to comment Share on other sites More sharing options...
aek Posted October 2, 2019 Author Share Posted October 2, 2019 Ok, so I doctored the flask with an inverted funnel and foil tape and got a nice jet of smoke..but still didn't work. This method in of itself is an artform which is going totake lots of patience/practice...which only makes me want to figure it out even more. I probably just need different glassware, dust seemed to clump and spit out through the plastic funnel. Link to comment Share on other sites More sharing options...
Phevo Posted October 8, 2019 Share Posted October 8, 2019 Sorry for the Kate reply, these are not the best molds to compare as they Are from two different types of silicone, but you can get a rough idea of what it looks like. The original aragonit shell has always been disintegrated, but not necessarily before leaving a good cast in the surrounding fine chalk particles, and that is were the cast is made. 1 Link to comment Share on other sites More sharing options...
aek Posted October 10, 2019 Author Share Posted October 10, 2019 I like this effect. Thank you @Phevo for posting. Link to comment Share on other sites More sharing options...
cngodles Posted March 13, 2023 Share Posted March 13, 2023 (edited) On 10/2/2019 at 11:10 AM, aek said: got a nice jet of smoke..but still didn't work. I've found that over time the temperature of the smoke matters. It won't coat/crystalize unless it is at a particular temperature. In my setup, when I heat the source, the smoke doesn't do much. But if I heat the glass tube between the source and the specimen, I get better results. I think it needs to be warmer. [source + heat] ======== [specimen] Doesn't work well. [source + heat] ==== [heat] ==== [specimen] Coats well. Also, moisture is a big deal. You can remove the coating by simply breathing on a specimen. On days where the house is humid, it is very difficult to coat and relocate the specimens for photography. Edited March 13, 2023 by cngodles 1 Fossils of Parks Township - Research | Catalog | How-to Make High-Contrast Photos Link to comment Share on other sites More sharing options...
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