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Thanks for the quick response Marq. I was hoping to have you chime in! Does orange peel begin to disappear as the paint cures to it's final hardness? It seems like the paint is showing less orange peel as it has longer to dry!



The story on orange peel is pretty straight forward and it explains why you would see a rise of the orange peel and then a settling back of the orange peel to a lower level.

Ok... so there is a coat of paint on the car, or bike or tool chest or whatever. And so we fall back to my lame ascii graphics to explain this :

Ok.. here is a fresh coat of paint applied to a surface

XXXXXXXXXXXXXXXXXXXXXX - recent applied paint layer
---------------------- - surface paint applied to

Now... when you add a new coat of paint on to this it looks like this :

NNNNNNNNNNNNNNNNNNNNNN - fresh coat of paint
XXXXXXXXXXXXXXXXXXXXXX - previous coat of paint
---------------------- - original surface paint applied to

Now... that XXXXXXXX layer is the one that will decide whether you get orange peel or not. Because the XXXXXXXXXX layer is actually two layers. If you were to look at it from a side profile :

0000000000000000000000 - outer skin of coating
xxxxxxxxxxxxxxxxxxxxxx - paint trapped between skin and subsurface
______________________ - original subsurface

What you see above is that the coat of paint as it cures forms an outer skin as it hardens.

The xxxxxxxxxx layer is the paint that is trapped between the outer skin and it is slower at curing and hardening because its curing time is slowed by the formation of the other skin. The carrier or gases have a harder and slower time evaporating out through the hardened outer skin.

That xxxxxxxxx trapped layer needs to reach a point of curing or hardening where it is no longer any curing happening. Otherwise it is still somewhat moist.

IF you slap a new coat of paint on the paint while only the outer layer of the previous coat is cured and its underlayer is still moist, the new coat of paint will weaken the tension or hardness of the previous layers outer skin.

AS the new coat of paint now begins to dry, it will be contracting and forming a new tension on its outer skin. But since the previous paint formation's outer skin has been weakened and it has a moist layer still trapped beneath it, this causes the lower layer of paints skin to contract and shift - this forms the orange peel

Soooooooo... one of the key things we harp on in this roll your own method is to make the paint/mineral spirit mix pretty thin.

Based on what I have just explained above you will see and be able to guess that if you are applying a superthinned layer of paint... there isn't as much paint being trapped between its curing and hardened outer skin and any paint trapped below it. HENCE the entire layer of thinned paint is able to fully cure and harden from top to bottom - without leaving a trapped moist layer beneath the outer skin.

When the coat of paint is rolled on too thick, you can almost guarantee that without a long drying time between coats of paint, you are guaranteed that moist layer is trapped underneath what appears to be a cured outer skin layer.

This whole story or concept is the key to success with the roll your own paint job and avoiding orange peel along the way.

Thinner is better because it helps you avoid any trapped moist layers that can become future orange peel sites...

And patience or properly timing your coats of paint is important to ensure that you have allowed enough time for the layer of paint to have evaporated its gases and formed a solid layer.

So the orange peel, when it happens, contracts the lower weakened skin and rises to its maximum height. Then as the trapped layer evaporates the gases or carrier out it retracts as the gases are expelled, until the lower layer is hardened and cured. But it is unable to return to a flat surface because it has bunched up the lower layers skin and hardened to its wrinkled shape.

Uh... I think I just put 20,000 people to sleep explaining the concept...

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Last edited by Marq; 05/06/08 09:40 PM.