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Building Tips and technical articles. => Paint and finishing => Topic started by: Ken Culbertson on February 28, 2019, 04:32:36 PM

Title: Undercoat Color
Post by: Ken Culbertson on February 28, 2019, 04:32:36 PM
I am planning on white wings and a red fuselage and stab.  My question is the undercoat color.  If I use white on the wings why not white as undercoat?  Seems like I might save a coat on the wings that way.  I can't add a whole lot of weight and both colors show through pretty badly.

Ken
Title: Re: Undercoat Color
Post by: Paul Wood on February 28, 2019, 04:49:31 PM
That's exactly what I did on this plane. I sprayed one coat of white on the entire plane and two coats over the area that would remain white. I expanded the two coat white area by a couple of inches into the area that I intended to paint red. That ensured I didn't have a light white area along the edges of the red/white transition after laying out the red design.

Paul
Title: Re: Undercoat Color
Post by: Ken Culbertson on February 28, 2019, 05:06:32 PM
That's exactly what I did on this plane. I sprayed one coat of white on the entire plane and two coats over the area that would remain white. I expanded the two coat white area by a couple of inches into the area that I intended to paint red. That ensured I didn't have a light white area along the edges of the red/white transition after laying out the red design.

Paul
Thanks!  I have done red w/o an undercoat and it took about 5 coats to cover the dark spots.
I will do it your way!

Ken
Title: Re: Undercoat Color
Post by: Trostle on March 01, 2019, 10:44:15 PM
A light gray undercoat overall works well for me.  Makes kit easy to see the small flaws which then can be filled with a mixture of the same gray and zinc stearate.  Acts like a really light-weight primer.  Makes it easy to then cover with white, or red or yellow without resorting to lots of coats to cover any unevenness of the underlying materials/color shades.

Keith
Title: Re: Undercoat Color
Post by: Randy Powell on March 05, 2019, 06:47:59 PM
Depends on the effect you want. With red, for instance, if you use white as an undercoat, it will tend to make the red much brighter. Black undercoat will make the red deeper and less bright. Gold underneath will give the red gold overtones. Just kinda depends on what kind of effect you want to create. Red is fairly transparent. Same for yellow.
Title: Re: Undercoat Color
Post by: Ken Culbertson on March 06, 2019, 11:55:57 AM
Depends on the effect you want. With red, for instance, if you use white as an undercoat, it will tend to make the red much brighter. Black undercoat will make the red deeper and less bright. Gold underneath will give the red gold overtones. Just kinda depends on what kind of effect you want to create. Red is fairly transparent. Same for yellow.
I am using Rustoleum Gloss White on the wings and Red and Blue for the fuselage and trim.  Using Rustoleum gray filler/primer for the undercoat.  It dries flat and shows flaws beautifully.  I am curious if anybody else has used this and if so how long before it will "powder" when sanded?  I am getting hints of powder at two days.   I am guessing 4.  That is just too long for filler.  Can a nitrate layer exist between two Rustoleum's and still not pull off with the masking?

This used to be simple. 4 coats of Sig Clear.  Light sanding with 400.  Sig Color, one coat per day, till you couldn't see the wood. Mask and add trim then 4 coats of clear.  Wait a week, wet sand, polish and fly.  AND, you did all of that with a 1" Camel Hair brush!

Ken
Title: Re: Undercoat Color
Post by: Paul Smith on March 06, 2019, 03:24:16 PM
The Randolph (Brodak) painting instructions say that both red & yellow are transparent and require a white undercoat.

Without the white basecoat no amount of red or yellow will look any good.

Furthermore (this my finding) more coats of red will make the color progressively darker.