why a varnish is more gloss with alcool ???

[BenTSH]

Hi, first thread


I've made a quick test with a Tamiya X22 acrylic varnish with just a few quantity BUT with around 30% or 40% of 95° alccol and the résult was very glossy with thickness feeling

Than I tried with only the varnish and the feeling is quite good BUT not as glossy and thick as with alccol and I 've used nearly the half of the 10ml bottle for a cigar size object ????????
I promess I haven't drank the 30/40% of alcool unused

Thanks by advance

 

[Mr.Micron]

I am confuse when you say thick , Thick to me means un-reduced but you are reducing it with the alcohol which makes it thinner and you build more layers or depth which is why it might look glossier then without reduction.

 

[BenTSH]

you are right, effectively my words are not precise enough, sorry...

For me thick means "with more depth" feeling

 

[BenTSH]

the "problem" is that I only use few varnish layer with the reduced test because I was worried about a less glossy effect and I was expecting a glossier effect with un-reduced

 

[Robbyrockett2]

Youve just discovered why we thin paint, and then do multiple light coats instead of one heavy one.

But.....do you really want a long boring explanation of why it does that?

 

[BenTSH]

Hi robbyrockett,

I love the long and rewarding explanation

same feeling about what happen physicaly ( why is better or not ) with sanding for paint or bonding

 

[Robbyrockett2]

Well , among other factors, the big thing is the way it dries.

It will dry on the surface first so you have this stage where the surface is a flexible skin floating on wet paint. As it dries it shrinks. If there is wet paint underneath that skin creates a little texture.

Next is the way the solids react. They are like little plates, with a thick enough film they can stick in just about any orientation. Then it dries with a lot more plates standing on edge. With thin films they lay down on each other like fish scales.

There's a balancing act here though. Too thin a paint, with too big a particle will act the same way, that can make metallics come out like sandpaper.

Sanding for a bond is easier.
Paint has two ways to bond, chemical and mechanical.

Sanding creates far more opportunity for both.

A theoretically perfect smooth surface 10x10cm has 100 cm2 surface area..

A sanded surface can have 1000 times that because of all it's peaks and valleys.

Chemical bonds usually rely on some relationship with electrons beyond the scope of explaining here.

Mechanical bonds are just that, essentially friction. I'm sure you've had to pull apart some stack of items like house siding that fit together well and felt the grip they had on each other. Same thing is happening on a microscopic scale with mechanically bonded paint.

Once that grip is stronger than the film of paint is over a given area, there's no peeling that paint off.

 

[BenTSH]

That's the way, uh-huh uh-huh
I like your answer, uh-huh, uh-huh
think about the song

More seriously: for you "the solids react" is the dryed paint/varnish ? I don't misunderstand ?


The thing crasy is when it is sanded with 1000 of higher you have a very smooth feeling which make me feel the paint will "slide" over it instead of bond but I understand it is a wrong feeling.

Do you recommand a grit for airbrush paint, another one for bond and a third for varnish ? Even if the bonded parts materials and kind of paints and varnishes influences probably the answer...

 

[BenTSH]

what do you think about 3M radial disc ? there are until 2500 grit




Visu 3D

 

[Robbyrockett2]

what do you think about 3M radial disc ? there are until 2500 grit




Visu 3D

Never used one but, looks like a mop sander. Basically only useful for something with lots of nooks and crannys. Like a carving. Its not going to give an even surface like blocking does on anything that you want to paint smooth.

 

[Robbyrockett2]

That's the way, uh-huh uh-huh
I like your answer, uh-huh, uh-huh
think about the song

More seriously: for you "the solids react" is the dryed paint/varnish ? I don't misunderstand ?


The thing crasy is when it is sanded with 1000 of higher you have a very smooth feeling which make me feel the paint will "slide" over it instead of bond but I understand it is a wrong feeling.

Do you recommand a grit for airbrush paint, another one for bond and a third for varnish ? Even if the bonded parts materials and kind of paints and varnishes influences probably the answer...

Solids are the part of the paint that doesnt evaporate, pigments and resin. They are finely ground particles mostly.

Yeah it all depends ,
Before primer can be anywhere from 80-240 depending on what it is.

Primer i will sand to 400 grit for most single stage paint. 600 For BC/CC.

prep to airbrush - 800- 1200 mainly depending on what type of paint is already there and thus, what goes back on top. Whatever the TDS for the clear says for blending.
If youre using 1000 and higher youre mainly depending on the chemical bond.

Treat the AB paint like basecoat, we dont want to sand it of course.

 

[BenTSH]

Well I need to sand lures so they are like a cigar or foot ball ( even if the section is more like a rounded rectangle ) and with sand paper I made planar faces or I have to spend hours for a good result so what sand tool could I use to sand homogeneously this kind of small shape

I've tried this too:

 

[BenTSH]

sorry: TDS ???

 

[BenTSH]

AB paint ( I guess Acrylic base ) never have to be sanded and is not able to be sanded or even polished between coats ( even if a long time between two coats is one day for example )