Questions about dope and thinner.
 

Hey guys, I am building a stick and tissue airplane. I have some questions about the dope and thinners used.

I went to my LHS to buy more Sig thinner because that is what I already have. Sig dope and thinner. But man-o-man, is the Sig stuff expensive. I looked at some other brands, Brodak for one. A quart of thinner for $2 bucks less than a pint of Sig. 8 ounces of Brodak dope for less than 4 ounces of Sig dope. I asked my LHS guy if I could use Brodak thinner and was told no, it won't work with Sig dope.

So, to my questions:

1) Are there any dopes/thinners from different manufacturers that are compatible?

2) What would happen if I used regular lacquer thinner with dope? Or paint thinner with dope?

3) If I have already applied Sig dope, and it has dried, could I later apply Brodak dope/thinner?

Thanks for the help! :)

RE: Questions about dope and thinner.
 

there are two type of dope nitrate and butylrate sig makes both,do not know what type brodak is,thinner by type should be compatable but have not tried it.the other thinners you mention will not work.thinner is cheaper in the larger sizes.I used to buy it in gallon cans for spraying.

RE: Questions about dope and thinner.
 

I have been painting for over 60 years> Lacquer thinner will thin but does not stick to well.Best stick with the same type of product such as Sig thinner with sig dope ect.I have recovered 35 real aircaft and 88 Stearman wings. I always stick with the same products
BOB MOORE

RE: Questions about dope and thinner.
 

I would say go with Bob's advice. I think his experience equals expertise.

I use cheap lacquer thinner to clean my spray guns, but I only mix Brodak thinner with Brodak dope for painting.

I have successfully used Sig nitrate under Brodak butyrate, but I've never tried Sig butyrate over Brodak nitrate.

I once painted some Sig silver butyrate trim over some Brodak butyrate and it produced a crackled texture; a bad reaction.

You cannot put any nitrate over any butyrate as far as I know.

I recently bought quart quantities of Randolph tautening nitrate and nitrate thinner from an aircraft supply company.

Brodak's dope is Randolph. So, you can use Randolph products with Brodak's dope. I seal and adhere covering with the Randolph nitrate and paint colors over it with Brodak butyrate. So far, it is working great. And, it's the most economical combination I can find.

Here's a tail done with Brodak butyrate colors. I still need to spray the final clear coats:

RE: Questions about dope and thinner.
 

Dunno, but was told two months ago at a S.A.M. meet that Randolph is only one really making dope any more. They seldom sell it under their label anymore. It is mainly canned for customers, like SIG. There are different blends available, which require different thinners.

I use common old Stit's Classic, for can pick up a quart, gallon, etc. in twenty minute drive. Is a bit thick, so needs thinning. Which they then sell as a generic brand in a gallon.

Wm.

RE: Questions about dope and thinner.
 

Thank you, all, for the information. [sm=thumbup.gif]

PS: awesome paint work, rainedave!!!!!

RE: Questions about dope and thinner.
 

CoosBay. Sig is not Randolph. Brodak claims that their dope is packaged by Randolph to their specs, but I haven't tried theirs yet. Normal dope thinner will NOT work with Sig nor Aerogloss (when it was around), and Sig thinner has eaten everything that I have tried to use for masking, including my Frisket paper, 3M blue tape, etc.

Les

RE: Questions about dope and thinner.
 

I've used Sig thinner with Randolph nitrate and Aerogloss, as well as Sig dopes, with good results. Never had any problems with tape or frisket. However, if you are going to try a mix of types/brands, best to do a test panel first. I tried to clean my spraygun, after shooting Aerogloss clear, with a hardware store laccquer thinner. Made cloudy jello[:o] which I cleaned up with Sig thinner.

RE: Questions about dope and thinner.
 

I have used Brodak and Sig thinners and dopes interchangeably without problems so far. They are not the same, but they do seem to be compatible. Dope thinners and lacquer thinners are a mixes of solvents and it's hard to tell what you're getting.

Cheap lacquer thinner works on nitrate dope but not very well on butyrate, and it will blush if it is humid. I assume the fact that butyrate holds up fairly well to nitromethane is related to the fact that it is fussier about thinners. Both Sig and Brodak retarders will work on either brand, nitrate or butyrate.

I think it's a good rule that anything that thins butyrate will thin nitrate. The reverse is not necessarily true.

Jim

RE: Questions about dope and thinner.
 

Thanks for the additional input, fella's.

Here is a little tidbit:

I had a jar of Aerogloss white dope. I used it to paint the firewall of a Sig Rascal ARF. So, I had this jar left over. I wanted some grey fuelproof paint for another plane, a Sig Four Star 60 kit I was building. Just for the heck of it, I decided to see what would happen if I tried to mix acrylic paint with the Aerogloss. As you know, acrylic is water based paint.

I added some black to the Aerogloss white dope. It mixed like it was made for it. I now have a jar of grey dope I use for engine compartments and cockpits.

RE: Questions about dope and thinner.
 

Don't you mean Acrylic Lacquer Tom? Sure doesn't seem possable that any water based paint would mix with dope?

RE: Questions about dope and thinner.
 

Acryllic is not necessarily waterbased, although it can be. I find it hard to believe that you could add a water based product to dope and have any type of success.

RE: Questions about dope and thinner.
 

I'd like to ask a question here rather than post a new question so close to this one.

I've used Superflite clear butyrate and clear Superflite thinner to seal my Koverall. It was applied with Stix-It by Sig.

I brushed on 3 base coats unthinned. They went on like honey but dried without brushstrokes. I sanded between coats and applied a final, thinned 50-50 coat and am now ready for color.

Supercoat, Aerogloss, etc., are all butyrates as far as I can tell. I have several gallons of Randolph in orange-yellow, dove gray, white and brown. These too, are all butyrates.

Will shooting my colors with Randolph's over the Superflite create issues? I always thought that butyrate was butyrate, regardless of manufacturer.

Also, would silver-doping prior to applying color be adviseable? I have a partial gallon of this as well with another brand that escapes me. it is butyrate though.

What are my alternatives to butyrates for color? Glo fuel, 4-stroke is my powerplant.

Here's what I'm using and what I have for color:

PM

RE: Questions about dope and thinner.
 

Once you have painted with butyrate, I'm pretty sure you shouldn't try to put anything else on top of it. Nitrate can be a base for other types of paint, but I don't think butyrate can. Therefore, the Randolph colors are probably your only option.

I'm not familiar with Superflite--where did you get it? My guess, like yours, is that Randolph will work over it--I've never run across butyrates that are not compatible--but I would test it on scrap first.

Jim

RE: Questions about dope and thinner.
 

Superflite has been around since 1949 or so...EAA-types know 'em well.

Here's their link:

http://www.superflite.com/Index.asp

Unfortunately, they have not replied to my repeated inquiries about other butyrate products over theirs.

PM

RE: Questions about dope and thinner.
 

Hey, they're as old as I am! Looks like nothing under a gallon, which I suppose is why I haven't heard of them. Someone at EAA might know because both dopes are used for full scale, but I would just try it on scrap. They probably work with the same thinners and they are probably compatible. Jim

RE: Questions about dope and thinner.
 

Buzzard bait,

I did get a reply from Randolph this afternoon, however...Here's their reply to my question:

Mr. Carner,

Believe it or not, we don't do compatibility checks much with Superflite,
Ceritfied coatings etc. In general it is not so much because we are trying
to promote our own sales, but you have real legality problems mixing dopes
in full sized, certified aircraft. The FAA frowns on such things since it
mixes STCs. Today, most full sized guys pick a system and stick with it,
all products are pretty good.

>From a chemistry point of view however, dopes and the thinners formulated
for them vary wildly. There is no standard, and each manufacturer makes
his own, tests it, and lets the other guys do the same. There are some real
horror stories out there of guys who use whatever is cheapest, or whatever
they can bum from their buddies.

So try it. You have a 75% chance that all will go well and about a 25%
chance that your beautiful Curtiss Robin's finish could look like cottage
cheese. Depends on how much of a gambler you are.

In the future, we suggest you pick a system, any system, and stick with it.

Thanks Jon

Looks like I'll stick with SIG products in the future, LOL...

PM

RE: Questions about dope and thinner.
 

Hey PM, that's a very cool reply from Randolph--thanks for posting it! I'm not surprised about the thinners, but I am a little surprised that the dopes could differ that much. I've used Randolph, Sig and Brodak interchangeably but they probably all come from the same hen house. Sooo...let us know!

Jim

RE: Questions about dope and thinner.
 

Nope. Black acrylic, from Michael's. The same stuff I use to shoot lexan car bodies. I beleive the bottle of black acrylic is still in my shed, sitting next to wear the Aerogloss bottle was. I will check tomorrow and take a picture of what I used.

RE: Questions about dope and thinner.
 

There use to be a compatibility chart somewhere here on types of dopes and such.

Butyrates must use butyrate thinner. Nitrates can use either nitrate or butyrate thinner.

Butyrates can go over nitrates but not the other way around.

Aerogloss is nitrate with some additive to make it fuel proof.

Acrylic is a term used to describe what the color particles are made of which is a man made product. It does not tell you the type of paint. You can have laquer, urathane,enamel, poyurathane, epoxie and such that use acrylic as a color base.

Laquer thinner some how "drys" out the dope. It was like oil and water they would not mix and the color lost its liquitity.

There is always someone out there who can brake the laws of physics and mix the wrong stuff up and make it work.

RE: Questions about dope and thinner.
 

I think that is exactly what happened here. ;)

As promised proptop, here are photos of the two products I mixed:

RE: Questions about dope and thinner.
 

AeroGloss is a nitrate-based dope and evidently, whatever composition the acrylic product is, they were "compatible". Betcha it wouldn't work with a butyrate, though, lol...

I gave up on trying to fathom all this crap out. It gave me a headache.

I went to WalMart, bougt a spray can of MinWax Polycrylic satin finish and commensed sparying the fin and stab of my Robin. This was after 3 coats of the Superflite butyrate, wet sanded between coats, to seal the weave.

The 1st coat produced a few pinholes so I was ticked, naturally. I wet sanded again with 360 and this knocked right through it. Using a satin over the glossy clear dope allowed me to "see" this, lol...

I applied another wet coat and this I'm allowing to set up over night before messing with it again. I had a test square that had Randolph over Superflite and to this I shot the MinWax, too. Once dried, I applied a top-coat a Krylon. Hmmm, 5 coats before the color. Yep, Im sure tired of using non-hobby related materials, LOL...

This is what happens when I ignore my rolls of Ultracote over in the corner and decide to do something, "different", :-)

I'll let y'all know if it works out. Otherwise, the Robin may be wearing the Ultracotes, yet.

PM

RE: Questions about dope and thinner.
 

I have Sig dope right now. So just for the heck of it I am going to make a small 1 ounce batch of 50/50 dope/thinner, and then to that I am going to add some acrylic white paint. It might turn out like cottage cheese. I don't know what it might do. I will find out and let you all know the results.

RE: Questions about dope and thinner.
 

Hummm....must be that "Licorice" is the secret ingredient!? :D[8D]
Hope it stays put in the long run...let us know if it's still fuel proof, or starts to flake, etc...cuz if not, you stumbled across sumpthin' there, aye!?:D

RE: Questions about dope and thinner.
 

Well, it has not had the engine running in the plane yet. But it definitley has stayed put and not flaked off after one years time.