Paint adherence problem

I just suffered the dreaded problem of lifting paint when removing the masking tape on my new Time Machine 40.

The base was built up with Brodak clear and Sanding Sealer over the tissued areas, and Brodak White Primer over the fillets (per Windy's video).

The masking tape used was Flex Mask red vinyl tape (I have 3M Fine Line and blue Plastic Tape that I'll try next).

The dope had thoroughly dried for about a week.

The finally sanding of the Sanding Sealer was done with 400 grit (perhaps too smooth ?).

The color paint was fresh Rust-olem white which was applied in one light fog coat, outgassed for 30 min, then a single "wet" coat, sufficient enough to flow and minimize orange peel. The spray can was heated by soaking in hot water prior to spraying. Spraying temperature was around 65 degrees (the instructions say a minimum of 50 degrees). The white had dried about a week before masking.

After the peeling was spotted, I used the heat gun to sucessfully remove the rest of the tape.

Any idea as to where I went wrong?

Cheers,

I would not use Rustoleum (or any other enamel) over Butyrate dope. Use nitrate only, and use one light coat of Enamel primer.

I had a yellow Chipmunk when I lived in OKC. It was painted with enamel over Sig butyrate dope. I peeled the enamel off with my fingers a couple months after completion.

The dope underneath was untouched.

Warren,
First some questions before the possible answer. Did the paint lift under the flexi-tape, or did the paint lift at the parting line between the tape/masked surface and the area you wished the color to stay on?

Reason I ask is this. During my use of Brodak dope on a recent project I found that the vinyl type tapes (red and blue kinds) when used for masking curves and the like tended to not provide for very good paint to tape separation properties. The dried dope tended to kinda' slide off the vinyl mask mediums, leaving a very ugly parting line at the masked edge. Normal masking tape used in the same area's of coverage did not exhibit this kind of tendency. The 3M brand masking tape of standard make-up pulled up as per normal, leaving a nice sharp edge between masked and unmasked areas.

I think that because the vinyl flexi tapes are of such smooth surface make-up, they offer less adhesion to the paint that is being sprayed over them. Because the paint does not adhere to the tape surface, it pulls off the tape during masking removal, and may start the beginnings of lifted paint at the surface of the model. If you continue to pull the mask up the lifting of paint at the model surface tends to follow along with this.

What I did to minimize this tendency was as follows. I liked the way the flexi tape takes a corner so I continue to use it for this purpose. But I also re-mask over this tape with standard 3M brand masking tape as close to the flexi-tape edge as I can get, to reduce the exposure of the flexi-tape to paint application. When it's time to unmask I very carefully pull the mask up at 90 degrees to the model surface at a min., and at more acute angles if possible. The hope is of getting a clean masked line between model surfaces. Should the dope pull off the vinyl flexi-mask tape and start to make a mess of things, I cut the pulled paint with a blade, and continue on with the un-masking as best I can. This can tend to leave an ugly demarcation line between your colors. To clean this edge up I've found that a single edge razor blade, laid flat against the surface, and slowly pulled along the raised paint edge will cut the pulled paint of the mask off the surface leaving a nice clean paint edge. Hope this helps some.

This is what happened to me. But I'm kinda thinking like you regarding the prepped surface. Brodak primer can be sanded to almost a shine if fine enough sand paper is used. Smoothing a little rougher then 400 may help reduce the pulled paint related to this. I'm going to try 320 as the final sand in the near future, ..give the dope a little more mechanical grip to the model/primer surface. Regards.
Tony

The paint lifting took place only UNDERNEATH the tape.

I understand what you mean about dope not sticking well to the vinyl tape as Ray Firkins, in one of his SN Finishing columns, complained about the same issue. The Rust-oleum is excellant in this instance, and sticks very well to the tape. The resulting masked edges are sharp and clean.

One thing I forgot to mention, is that I minimize the handling of the surface to be painted, and I wash the area down with Prep Sol and alcohol just before spraying.

Cheers,

Warren,

If this is Warren Wagner, Please send your email address. The one in pampa dosn't work and the Stuka Stunt does not show.

Jerry

[email protected]

At the risk of being rude, crude and socially unacceptable, "Why do you think they call it DOPE?"

While I still use dope to seal wood inside the fuse, cowl or anywhere I think oil will penetrate, it is still "stone axe and bear skin" technology.

If you feel that you MUST use dope, then use nothing but dope and don't let the tape stay on it for more than a couple of hours.

It would also help to move to the desert to avoid humidity and the resultant "blushing". Oh, and try to build only planes that don't have any concave surfaces, such as fillets,etc.

Hope this helps and good luck.

I'm with you.

DMoon

Well for what it is worth the problem is not the dope or the Rustolium paint. The problem is using the two of them together. There are not many paints that will go over butyrate dopes. Some polyurethane’s and epoxy paints will but the choice is very narrow. Nitrate dope is formulated differently than butyrate and it will accept enamels and other types of paints to be applied over it. For those people that want a quick and durable paint job try the following method.

From bare wood give the model 3 coats of nitrate dope and lightly sand the model between each coat. Let the nitrate dope cure completely for 24 at least hours. Next, spray on a coat of Top Flight Lusterkoat primer and allow to dry overnight and lightly sand with 320 sandpaper. Choose whatever color you want of Top Flight Lusterkote and apply three to four very light coats. What you want to do is add just enough paint to make the color opaque. Do not apply heavy coats because this will add too much weight. All enamels, polyurethane’s, and epoxy paints are heavy so they must be used sparingly.

The above method works great on profile model where the wings, stab, and elevators are covered with iron on plastic films.

I hope this helps,
Mike