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Building Tips and technical articles. => Paint and finishing => Topic started by: Tim Wescott on June 18, 2023, 10:40:06 AM
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Just how incompatible are Randolph and Certified dopes?
I have a ton of Sig color, which I understand is relabeled Certified. The last plane I finished I bought a quart of Certified clear for the undercoats, and that worked just fine. I have a plane I'm starting to finish, which has a few coats of Certified clear on it -- but I'm not sure if I can get any more (please do not address the availability issue here -- comment on this separate thread instead (https://stunthanger.com/smf/paint-and-finishing/certified-dope-availability/)).
What happens if I switch over to Randolph dope to finish the under-layers, then use Sig colors on top? Will I have terrible adhesion problems, or will lower layers wrinkle -- or will it turn out fine?
If I can't put Randolph products in between layers of Certified, any suggestions on what to do?
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Its all butyrate. I would proceed if it were me. All the issues you mention can still happen even if its all one brand.
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All the issues you mention can still happen even if its all one brand.
Uh -- thanks. That makes me ever so confident. I probably only have two or three years of finishing with dope spread over 45 years of modeling. On the one hand, I haven't seen a hint of this sort of problem -- but on the other hand it's all been with Sig products.
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Just how incompatible are Randolph and Certified dopes?
I have a ton of Sig color, which I understand is relabeled Certified. The last plane I finished I bought a quart of Certified clear for the undercoats, and that worked just fine. I have a plane I'm starting to finish, which has a few coats of Certified clear on it -- but I'm not sure if I can get any more (please do not address the availability issue here -- comment on this separate thread instead (https://stunthanger.com/smf/paint-and-finishing/certified-dope-availability/)).
What happens if I switch over to Randolph dope to finish the under-layers, then use Sig colors on top? Will I have terrible adhesion problems, or will lower layers wrinkle -- or will it turn out fine?
If I can't put Randolph products in between layers of Certified, any suggestions on what to do?
aircraft spruce website says not to mix certified and randolph products because its not always compatable https://www.aircraftspruce.com/catalog/cspages/dopesthinnrsolvents3.php
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According to my local airport supply store, the difference between Brodak, Randolph and Certified is the price alone.
His price for Certified is the least high of the three. The words "lowest" and "cheaper" do not apply to any of these products.
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I use largely Randolph clear under and over Sig colors with no issues. For a while I used Certified clear which was OK but two semi-issues;
1. Certified has a LOT more solids in it. It fills very well and fast but can end up a lot more heavy if not careful. Randolph is thinner out of the can but I still cut it about 1/3 rd rather than 100% with the Certified.
2. Certified as a top coat over Sig color is fine except it doesn't really etch and adhere to the color. Where damaged or chafed the clear will peal off like stretch wrap. The solvent in the clear doesn't seem to have any effect on what is underneath.
Now with the apparent demise of Sig dope I am using Randolph throughout. The only downside is that you'll have to buy your colors by the quart instead of smaller quantities. I don't know much about Brodak dopes other than they give me a headache right away unlike the others so their solvent must be something different than the rest.
Dave
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According to my local airport supply store, the difference between Brodak, Randolph and Certified is the price alone.
His price for Certified is the least high of the three. The words "lowest" and "cheaper" do not apply to any of these products.
$92 dollars for a quart of certified thinner :o
https://www.aircraftspruce.com/catalog/pnpages/09-11900.php
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$92 dollars for a quart of certified thinner :o
https://www.aircraftspruce.com/catalog/pnpages/09-11900.php
92 dollars for a quart? that must be a mistake.
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92 dollars for a quart? that must be a mistake.
im sure it is..a gallon is only $72
im using randolph clear nitrate,sig super coat clear and brodak color and finnishing with brodak crystal clear on the same plane with no problem,im pretty sure its all made by randolph,i know the brodak is and pretty sure the sig is also randolph too...
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im sure it is..a gallon is only $72
im using randolph clear nitrate to attach the silk then sig supercoat clear to tighten the silk and then brodak color and finishing with brodak crystal clear on the same plane with no problem,im pretty sure its all made by randolph,i know the brodak is and pretty sure the sig is also randolph too...