Author Topic: SIG dope compatibility with Brodak/Randolph (Read 15024 times)

Steve Thompson · « **on:** July 29, 2024, 04:12:33 PM »

I've read for years about the compatibility between SIG, Brodak, and Randolph dopes but have never had to worry about it as I used only SIG dope products. Although I have a near lifetime stash of SIG (I hope I live that long!) I don't have any white.

I am now to the paint stage on a new build and been doing a deep dive into compatibly of different brands. Airplane was covered with SIG Nitrate dope and am ready for Butyrate color coats, etc.

I know this has been covered many times, but I am looking for a little reassurance and info before stepping into (for me) uncharted water. Rather than screw up what is so far a nice build, I am curious what the current consensus is on compatibility. So...

Would Brodak or Randolph dope cover over SIG nitrate, and then allow a good bond to other SIG butyrate colors and LiteCoat clear?

Would getting white pigment from an auto body paint supplier and mixing in LiteCoat be a good/better plan?

Dan McEntee · « **Reply #1 on:** July 29, 2024, 07:30:17 PM »

I think both SIG and Brodak dope is based off Randolph's. All SIG color dope were made with Litecoat as a base. I think if ample time is allowed between coats after a good sanding, I don't think you will have any problems. I have a memory of reading on here somewhere about Brodak has several different white dopes?? You may want to research that on the forums here. I think it was more an issue of how it affected other colors that went over it??? If your overall base color coat will be white, try the "doping your dope" trick on your clear coat build ups. Put just a dash of white in your clear as you apply it. Over the course of doing your build up and sanding in between, you will start to get a white colored airplane as you go along. Then you might only need one even final coat to cover nicely. I have seen several examples of this and it's a great way to keep excess weight creeping into the final finish. The model doesn't need to look like a refrigerator!! Getting some Randolph white might be your best bet. Adding pigment to your Litecoat might take some experimenting on how much you add to get decent coverage. A quart of Randolph's might work out better for you economically over time also.
Type at you later,
Dan McEntee

wwwarbird · « **Reply #2 on:** July 29, 2024, 09:12:39 PM »

I've mixed, matched and jumped around every which way using all three brands countless times over the years with no issues at all. I have no proof but I do feel like the pigments are heavier with the Brodak/Randolph brands, in my experience they seem to cover much better than Sig. For that reason I haven't purchased any Sig dope for years.

Dave_Trible · « **Reply #3 on:** August 08, 2024, 07:08:33 PM »

I've used Sig and Randolph dope over/under each other many times with no problems. I'm not sure about Brodak (or ALL Brodak). Brodak can give me a headache to use where the others don't. I assume they have a different thinner base that doesn't agree with me. Also I bought a few CLEARANCE bottles of Brodak color dope a while back that had "Randolph" in smaller print on the label indicating to me that they may have used more than one source for their dope "paint" as they have advertised it. I don't think I'd try mixing most of it with Sig or Randolph. Since Sig is no more I've gone over to Randolph exclusively which solves any problems.

Dave

doug coursey · « **Reply #4 on:** August 09, 2024, 06:52:34 AM »

WINDY WORKED WITH RANDOLPH TO DEVELOP BRODAK PAINT...HE LIVED CLOSE TO RANDOLPH ...BRODAK PAINT HAS MORE PIGMENT THAN SIG. I HAVE USED RANDOLPH,SIG AND BRODAK TOGETHER WITH NO PROBLEMS..

Motorman · « **Reply #5 on:** August 09, 2024, 09:59:26 AM »

I would try the white pigment plan, if only to make use of your stores. Just be sure the pigment is the right type for the dope and, of course experiments on how much to add would be in order.

MM

Steve Thompson · « **Reply #6 on:** October 20, 2024, 01:42:00 AM »

Here is a report after painting:

The Brodak white showed no compatibility/adhesion problems with the SIG Nitrate and Butyrate dopes.

This is order of application:

SIG Nitrate to cover with SIG Koverall.
SIG Clear Butyrate.
Brodak White thinned with SIG thinner.
Two trim colors (SIG Light Red and Clipped Wing Blue)
SIG Litecoat clear.

Plane is a SIG Skybolt with box paint scheme.

The clipped wing blue colors were from SIG rattle cans, packaged in October of 1989! I purchased them from Brodak as close out sale items about 15 years ago. Figured I would drain the cans and use in a spray gun. The cans sprayed really nice and no gun to clean. I have three other colors as well and happy to think they might all be viable.

Also painted a 38 Special with the clipped wing blue. Didn't use the white. The blue covered nice as a base color/final color. Trim colors to follow.

This was about the last of 70 F weather here. Cold and rain incoming.

Only obstacle was painting outside while gnats were having a big fall swarm event. 7 gnats required a quick dig-out and fill with more paint.

I am impressed that the 35-year-old SIG rattle cans worked so well.

Author Topic: SIG dope compatibility with Brodak/Randolph (Read 15024 times)

Steve Thompson

SIG dope compatibility with Brodak/Randolph

Dan McEntee

Re: SIG dope compatibility with Brodak/Randolph

wwwarbird

Re: SIG dope compatibility with Brodak/Randolph

Dave_Trible

Re: SIG dope compatibility with Brodak/Randolph

doug coursey

Re: SIG dope compatibility with Brodak/Randolph

Motorman

Re: SIG dope compatibility with Brodak/Randolph

Steve Thompson

Re: SIG dope compatibility with Brodak/Randolph