Brodak Dopes

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bernomatic
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Brodak Dopes

Post #1 by bernomatic » Mon, 20 Jun 16, 22:06 pm

Originally when I was starting airbrushing, I was going to use strictly dopes. My experience using them was, shall we say, less than pleasing, so I tried the Createx. Now that I think I have the Createx mastered, I may have to revisit the Brodak dopes.

One of the things that I have found can be frustrating in starting airbrushing is the wealth of some information which leaves out small details. Some may have found some of the information I wrote in the Createx thread extraneous. But these are exactly the type of things which made my initial attempts so frustrating. Barely anyone talks about size and it's relation to air pressure and the amount to which you have to thin something (other than the common rule of thumb to thin till it has the consistency of 2% milk)

Anyways, the major reason I gave up spraying the dope was the lack of a nearby supplier of Brodak dopes and the extreme amount of thinner I was going through for thinning and clean up purposes. Maybe if the dopehead GH could give us his recipe for a home brew dope thinner, if it's chea enough I'll go back to trying airbrushing the dope. :idea: :ugeek:
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Ghrocketman
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Re: Brodak Dopes

Post #2 by Ghrocketman » Mon, 20 Jun 16, 22:28 pm

Ok...
I guess I should post "my recipe" for butyrate dope thinner here in addition to having it over on YORF.
This thinner recipe applies ONLY to Aero Gloss, Sig, Brodak, and full-scale aircraft Randolph Dope (which is what Brodak is, repackaged in smaller quantities). This recipe does NOT apply to old Testors Butyrate Dope which needs a MUCH different formula.
The BEST overall recipe for 'generic' weather conditions is as follows:
25% Toluene (sometimes called Toluol)
25% MIBK (Methyl Iso-Butyl Ketone)
25% MEK (Methyl Ethyl Ketone)
25% Acetone

All of these chemicals can be found at Home Depot/Lowe's EXCEPT the MIBK which can be hard to find unless one has a specialty paint shop in your local town.
If you cannot get ahold of MIBK, the formula I would use is below:
35% Toluene
35% MEK
30% Acetone

In some localities it can be hard to find Toluene- if that is the case, one can substitute Xylene ( sometimes called Xylol ) which is often easier to find.

If one is having a 'blushing' problem due to high humidity, increase the % of Touene or Xylene in the mix in relation to the other chemicals...that will slow down the drying time and reduce the likelihood of 'blushing'
If one wants a quicker drying time in dry humidity conditions, one can increase the Acetone %.

If one was interested in not having to 'blend' a proper thinner and just use one solvent, get Toluene. This will double the drying time, but will work. For some reason using straight Xylene will NOT work...have not figured out why.

All these blends can be a somewhat moot point however. If one has a GOOD Automotive paint supply in your area, AUTOMOTIVE Lacquer thinner from DuPont or Ditzler/PPG will work if it does NOT have any Methanol in the formula. Hardware store 'Lacquer thinner' will ABSOLUTELY NOT WORK ! That crap ALWAYS contains Methanol and WILL ruin ALL Dope. Dupli-Color also STUPIDLY puts Methanol in their Lacquer Thinner that is easily available at moist generic Auto Parts chain stores...don't use that crap either.

If one needs to thin old Testors Dope, the correct mix for that stuff is 50% Ethyl Acetate, 25% Acetone, 25% MEK.
Testor's Dope thinner MUST contain at least 50% Ethyl acetate or it will 'gel' the dope and ruin it.
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Re: Brodak Dopes

Post #3 by bernomatic » Mon, 20 Jun 16, 22:50 pm

Thanks, I knew we kept ya around for something
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Re: Brodak Dopes

Post #4 by Ghrocketman » Tue, 21 Jun 16, 02:19 am

LOL.
The most economical way to thin Butyrate Dope really is to buy DuPont or Ditzler Lacquer thinner. I think a whole gallon is only around $30.
Of course a gallon of Toluene is only about $20.
If you have no local source of automotive lacquer thinner, for the cheapest possible good mix I would get a pint each of Toluene and MEK or Toluene and Acetone and just combine them to make a quart of thinner. The Toluene/MEK mix would dry considerably slower than the Toluene/Acetone mix. If you spray in high humidity, definitely go with Toluene/MEK over Toluene/Acetone. This will prevent blushing of dope. Either of these mixes is considerably better than just straight Toluene, but not as good as the above 4-ingredient or 3-ingredient mixes.
When I shoot dope from an airbrush or small spray-gun I typically use 2 parts dope to one part thinner...if the project is really big, I may use a little more thinner to cut the cost of the paint job a bit.
Remember to NOT use dope on plastic parts unless one either first coats them with almost impossible to find long-discontinued Pactra Prep primer, real two-part Epoxy primer, or several (at least 5) coats of automotive Lacquer primer. Otherwise the plastic will craze and/or warp.
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Ghrocketman
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Re: Brodak Dopes

Post #5 by Ghrocketman » Tue, 21 Jun 16, 02:33 am

Lately myself I have been using a 50% Toluene, 25% MIBK, 25% MEK mix and leaving out the Acetone completely due to the high humidity we have here in Michigan.
Whenever the humidity is high, you want to SLOWWWWWW the drying time of Dope or Lacquer to avoid blushing/fisheyes.
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Re: Brodak Dopes

Post #6 by bernomatic » Sat, 11 Feb 17, 19:04 pm

OMG :) :) :D :D :D :D :D
I finally got enough of the ingredients GH mentioned to mix one of the cocktails he described. I couldn't find the toluene, but Home Depot did have the xylene so I went with a 35% Xylene, 35% MEK and 30% Acetone. It worked much better than the Brodak thinner I have bought in the past at $12.00± per pint and cost much less also.

It made my day in that when I did a test painting on some scrap parts I felt like this is what I was expecting from airbrushing with dopes. Now some of the instructions and practice in other airbrushing techniques may account for a part of this feeling, but when it came to the cleaning up of the airbrush of the dope, a task quite frankly I have thought of as akin to cleaning up an upper decker, with this concoction it was a breeze. 8-)

I can't wait to try it out on a properly prepped rocket and see exactly the type of finish I get. Needless to say I have high expectations. Damn, I might have to apologize to GH for all the bad things I've said about him over the years........ :? nah. And seeing as he deems it beneath him to visit us anymore he may never know. ;)
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Re: Brodak Dopes

Post #7 by bernomatic » Sat, 11 Mar 17, 17:00 pm

Ghrocketman wrote:Lately myself I have been using a 50% Toluene, 25% MIBK, 25% MEK mix and leaving out the Acetone completely due to the high humidity we have here in Michigan.
Whenever the humidity is high, you want to SLOWWWWWW the drying time of Dope or Lacquer to avoid blushing/fisheyes.


So the question now becomes:

If I am using the 35% Xylene, 35% MEK and 30% Acetone mixture and the humidity in the bunker (basement) with the new spray booth is somewhere around the 25%, should I increase the percentage of Acetone, or one of the other ingredients?
Or get the MIBK?
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Re: Brodak Dopes

Post #8 by bernomatic » Mon, 17 Jul 17, 03:46 am

Well I was spraying the Midget today and running into problems. I was using the new Master airbrush I purchased that came with three different needles/nozzle sizes. I was using the the 0.5mm needle/nozzle and ran into some troubles. After a while, the airbrush started spitting globs. While frustrating, I just cleared the nozzle more frequently and continued on. A little while later, I noticed that the dual action wasn't working correctly. I would press the trigger to start the air flow, and it would immediately start spraying dope, like it was a single action. I was close to finished with the coat and just motored on till I was done. Initially I thought the thinner or dope had eaten one of the O rings, when I started cleaning the brush, I came across the reason. The dope was drying and caking on the nozzle not allowing the needle to fully seat. I cleaned the airbrush up and ran ran some alcohol through it and everything was working again. The brush was only blowing air in the first action mode like it should.

So I came to the Starport thinking to add to this thread and started to read through GH's posts to see where the thread was left. During the read through, I came across GH's advice on humid days,
Lately myself I have been using a 50% Toluene, 25% MIBK, 25% MEK mix and leaving out the Acetone completely due to the high humidity we have here in Michigan.
Whenever the humidity is high, you want to SLOWWWWWW the drying time of Dope or Lacquer to avoid blushing/fisheyes.

While the humidity in the Rocket Bunker has been steady around 50%, the main basement area where the spray booth is probably is slightly higher. I expect the Acetone just evaporated and the dope was clogging the nozzle because of it.

On the second coat of the night, I added more Xlyene and MEK and while the clogging didn't stop, it was noticeably less. I also noticed that the dope would dry almost instantly (within 1-2 seconds) upon contact with the rocket. I'm going to have to experiment some more with the mixture.
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