Re: Re: covering with mylar

From: Don Slusarczyk <don_at_slusarczyk.com>
Date: Fri, 29 Apr 2011 00:15:20 -0400

On 4/28/2011 8:29 PM, John Kagan wrote:
>
> y reference to "relatively heavy" was intentionally vague.
>
> I covered a wing and prop using the solution wicking method and surprised at how overweight they were (I remember something on the order of several hundredths of a gram too fat).
>
> The next set I did using the activation method and got better results. That's the extent of my scientific analysis.


It is easy to get heavy for a few reasons.

1) to strong a solution
2) too much applied

I found that for different films a different solution had to be used.
For heavier films like polymicro (0.9 micro) I needed a stronger
solution than for Y2K. What I would do is take one of those small jars
that are about 1" in diameter and about 1.5" tall (~3/4oz or so) then
spray 3M77 in the bottle for about 3-4 seconds. Then fill to about 3/4
full with TCE then shake it vigorously. I would then take a piece of
1/16" sq wood about 3" long and lay it on the film. Then take a brush
and apply the solution and let it dry for at least 30 minutes. Then pull
on the piece of 1/16 to see how much force to pull it from the film. If
it comes off easy then add a quick squirt of 3M77 and try again. Too
strong add more solvent. Typically I would keep thinning until it became
too weak then add in one quick squirt of 3M to bring it back up. For Y2K
the solution was very thin like 10:1 or maybe even more. For heavier
films I had to make a stronger solution like say 7:1. I recall that the
stronger solution has a slight milky haze and the thinner solution for
Y2K looked essentially like pure solvent. In either case, if you rub the
soluton between your fingers you will not feel any tackiness.

Where the weight really comes in is if you use a strong solution when it
is not needed combined with over application. All that is needed is to
apply a small drop from the end of a brush to the outside of the outline
then let it wick a few seconds then apply another drop and so on. It is
very much like how applying microfilm with water was/is done. If one
drop wicks 1.5 inches in each direction then the next drop is applied 3"
away. Then tendency is to apply the drops too close to each other or
worse continuously along the outline. The excess glue just gets soaked
up into the wood. You are better off to apply the drops farther apart
then go back and fill in the missing areas. I cover wings upside down
(with the film on a frame) so after I have gone around the outline with
the solution, I flip the frame over and look to see if some spots are
missed. You can see where the film is attached to the wood or not pretty
easily if you look at an angle with good lighting. Once I am happy with
everything, I let it dry for an hour or so before messing with it.

Don S.
Received on Thu Apr 28 2011 - 21:22:40 CEST