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Bones: The First Coat is the Difference


Wren
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Another reason I suspect why spray primers are so random with Bones is because of variances in how close you hold the nozzle when spraying.   Let me explain...  No, let me sum up. :)

 

I was watching a Black Magic Craft video where he said people were having issues spraying on foam for terrain where it would melt the foam.  He demonstrated that if you hold the nozzle to close while spraying it would melt, but if you held it farther away (I think he used the distance on the bottle instructions) that it would not.  The reason, he posited, was because if you are to close the propellent doesn't have time to evaporate.  If you hold it far enough away it gives the propellent time to evaporate and just leave what it is carrying to hit the item at the end.   Perhaps this is what happens with bones and rattle can sprays?

 

The problem is, there are way to many variables to control.  Temperature, humidity, distance, type of propellent and who know what else that its impossible to control them all in a reliable way.  Which is probably why the results people have are so all over the place.

Edited by Rignes
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Melting Sprues to Recast as Warhammer 40K Parts

On 10/6/2020 at 1:26 AM, Foxden Racing said:

This is some hardcore thread necro, some super hardcore account necro, and it probably came up years ago somewhere in the middle of the topic, but...I've done a lot of digging in MSDS tonight, the subject came up during Dr. Faust's stream and my brain just would not let go.  Thought y'all might find it useful.

 

The 'sticky bones' culprit appears to be Toluene.  It's a common ingredient in US-produced (and produced-in-the-US-under-license) spray paints/primers as the nozzle-friendly solvent...and it dissolves / reacts with PVC, which is a key ingredient in Bones.  Spray primers made overseas like Tamiya and The Army Painter seem to prefer acetates instead, but I don't have access to a huge swath of MSDS (just Krylon, RustoleumArmy Painter, and Tamiya) to go hyper-analysis on it.

 

3 hours ago, Rignes said:

Another reason I suspect why spray primers are so random with Bones is because of variances in how close you hold the nozzle when spraying.   Let me explain...  No, let me sum up. :)

 

I was watching a Black Magic Craft video where he said people were having issues spraying on foam for terrain where it would melt the foam.  He demonstrated that if you hold the nozzle to close while spraying it would melt, but if you held it farther away (I think he used the distance on the bottle instructions) that it would not.  The reason, he posited, was because if you are to close the propellent doesn't have time to evaporate.  If you hold it far enough away it gives the propellent time to evaporate and just leave what it is carrying to hit the item at the end.   Perhaps this is what happens with bones and rattle can sprays?

 

The problem is, there are way to many variables to control.  Temperature, humidity, distance, type of propellent and who know what else that its impossible to control them all in a reliable way.  Which is probably why the results people have are so all over the place.

 

Both of these sound like great educated guesses - it might be that Black Magic Craft's demonstration of the difference that a little distance makes actually shows something going on with the Toluene:  either it evaporates a bit before hitting the target, or some other reaction has more time to take place which takes the "bite" out of the reaction.  For whatever it's worth, BMC is Canadian, and tries a few different brands of paint in his spraypaint available to him locally, with pretty similar results:

In a similar vein, Miniature Hobbyist actually makes deliberate use of the chemically vaguely similar Acetone (in that it is another volatile industrial hydrocarbon solvent and main component of such things as nail-polish and paint remover) to melt plastic Warhammer 40K sprues down into "Ooey Gooey Spruey Stuff" that he then uses to craft the stuff in various ways into miniatures and miniature terrain:

  • Miniature Hobbyist:  "Top 40 Uses for Warhammer 40K Sprues"  (several of these involve dissolved sprues, extruded through syringes, flattened into panels, pressed into molds, etc.)

Both Toluene and Acetone are aggressive and volatile solvents that will dissolve plastic, and both are pretty nasty, toxic stuff.  I haven't tested it, but if Acetone does that to Warhammer 40K plastic, and Toluene does that to Styrofoam, I can imagine either of these solvents doing some strange and terrible stuff to Bonesium!  On the understanding that a major component of Bonesium is PVC, this site indicates that PVC does, in fact, react badly to both chemicals:

 

For whatever it's worth, the Warhammer 40K sprue plastic is apparently "polyethylene or hard polystyrene, depending on the model", and Styrofoam is "foam polystyrene" plastic.  Evidently, both solvents also have Severe Effects on polystyrene, but polyethylene does seem to get along with Acetone (so evidently, those sprues are more than likely polystyrene!)

 

AND, both Acetone and Toluene are common components in spray-paint, as solvents.

 

In short, the solvents acetone and toluene - common spray-paint thinners - probably won't get along great in large amounts with Bonesium, but Black Magic Craft seems to be getting good results on something as delicate as Styrofoam by spraying from a safer distance, in a light dusting in multiple coats to keep from overwhelming the plastic, which sounds like a plausible way to get success from spray-painting Bones, too!

 

The next time I want to spray-prime some Bones, I'll test it out and see what happens.

 

 

Edited by YronimosW
At war with chemistry.
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