Re: Yellowing Clear Dope Problem

Stunt1

From: Robert E Lampione
To: [email protected]
Cc: Bob Elaine Brookins ; John Brodak
Sent: Thursday, February 26, 2004 4:43 PM
Subject: Re: Yellowing

Hello Crist Rigotti,

In reference to your yellowing problem with "Brodak Clear" dope. I happened to spray the clear coats on an airplane for a friend in the last 6 months and noticed the same problem. His base coats/colors were white, black and some red and silver. We immediately thought the same thing. I compared his Brodak Clear with some Randolphs and Sig that we had on hand and also some Certified Clear ( a brand carried by Aircraft Spruce, also like Randolphs, makes paint for real airplanes). All were clear clear with the exception of the "Brodak Clear". It was very obvious to us all that this had a yellow cast to it.
I know from dealing with Randolphs products through the years that they, as a company, make three kinds of clear dope. They make their clear in three versions. One has a blue tint to it, one has an amber tint to it and then they make a clear clear. I wonder if John Brodak was not aware of these differences, Randolph who makes the clear for John, only he gets it in 55 gallon drums, may have inadvertently sent him some amber colored clear which definitely goes on with a yellow cast to it, and his not being aware of this problem.
I am copying John on this "E" mail to you to make him aware of this situation. You may want to call him to see if he has had other complaints of this problem, because I have heard this story to many times already.

I remain yours in STUNT,

Mr. 69 NATS

Bob Lampione

If that is the same blue tint stuff I had years ago, it will shrink tight enough to but a bend in a 2" steel bar.

Jake

You guys are worrying me, I am one or two sandings away from clear on my Skylark and have a gallon of clear I bought at Brodaks contest last year, looks like clear clear to me. Hope this, as Len said was a problem left over from the batch a couple of years ago.

I started finishing a white plane using Brodak clear that I purchased at least two years ago. It looks water clear when poured into a clear glass container but had a definite yellow cast after sprayed on and cured. I have used Randolf dopes for years on full scale aircraft and foud the clear clear to also yellow over light colors without being noticable over darker colors. The Randolf tinted clears are special purpose dopes and are not very suitable for our modles as they don't have enough plasticisers in the batch and will continue to shrink sufficiently to bend a steel bar.

The "Big Boys" don't put clear on as a top coat as we do, so the tinting was done by Randolph and others to distinguish one type of dope from another. (Just like the aviation fuels are also tinted for the same reason). I was thinking that the non-tautening was green tinted, but my recollecton may be wrong. At any rate, they do have a clear without any tinting in it and the new Brodak dope should not yellow. That one batch, however was...bad.

spray some on a test strip and wait a week before using.

>silver. We immediately thought the same thing. I compared
>his Brodak Clear with some Randolphs and Sig that we had on
>hand and also some Certified Clear ( a brand carried by
>Aircraft Spruce, also like Randolphs, makes paint for real
>airplanes). All were clear clear with the exception of the
>"Brodak Clear". It was very obvious to us all that this had
>a yellow cast to it.

Bob;

Do you have any experience with the Certified Coatings dope carried by Aircraft Sprce and Supply? I would be interested to hear the results.

Bob K.