DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Painting Forum > which is better for indoor touch up acrylic or vinyl latex?




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Old 12-03-2009, 08:02 PM  
diyonthefly
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what i think i've learned about paint is that it's all about "rocks" suspended in binder. flat paint has more "rocks", i.e. extender pigments, than gloss paint, which causes more whitening effect. there are alot of things to consider when you want to do touch up work. i think your explanation on light properties is the key to it all.



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Old 12-03-2009, 08:43 PM  
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your making me think creatively. can you imagine a paint that is almost completely transulent, like just translucent plexiglass binder with added material that creates a glass effect with spotted elements scattered about. like looking at water on the wall with little fragments. sorry if i'm getting carried away. understand, master, create. i know i have a long way to go, but i can dream...i think you have inspired me.



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Old 12-04-2009, 05:17 PM  
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Originally Posted by diyonthefly View Post
Nestor:

your making me think creatively. can you imagine a paint that is almost completely transulent, like just translucent plexiglass binder with added material that creates a glass effect with spotted elements scattered about. like looking at water on the wall with little fragments. sorry if i'm getting carried away. understand, master, create. i know i have a long way to go, but i can dream...i think you have inspired me.
You can buy transluscent paint now.

Most paint companies no longer provide coloured tint bases. Years ago, if you wanted a burgundy paint, they would take a red tint base and tint it black (or darker anyhow). Typically, paint companies only provided tint bases in yellow, red and sometimes brown. Nowadays, because they can now add more colourant without screwing up the film formation process, paint companies only provide white, pastel, medium, and deep or "accent" tint bases. If you want a burgundy paint now, they take a deep or accent tint base and pour lots and lots and lots of red and some black colourant into it to make it dry to a burgundy colour. If they didn't add those colorants, then the paint would have no colour.

That doesn't mean the paint would dry clear. Any extender pigments in the paint, even clear extender pigments like pulverized silica sand, would reflect and refract light within the paint film to give it some opacity and make it transluscent. The more extender pigment in the paint film, the flatter the gloss and the more opaque it will dry. So, you can buy a colourless transluscent paint now. Just as for a dead flat black paint, but tell them not to put any black colourant into it. The result will be a flat transluscent paint with no colour.

You could probably add glitter to that paint before shaking it, but I don't know how well that would work. You may end up with clumps of glitter in your paint.

That's cuz the size of the colour pigments in house paints is a lot smaller than you're imagining. A "micron" is a million'th of a meter, or a thousandth of a millimeter.

A typical human hair is 100 microns in diameter.
The smallest thing visible by the naked eye is about 20 microns in diameter.
The coarsest extender pigments used in primers is about 10 to 20 microns in diameter.
A red blood corpuscle is about 5 microns in diameter.
The coarsest inorganic pigments like yellow oxide, red oxide and brown oxide are typically around 1 to 2 microns in diameter.
Organic pigments, like red, blue and green are typically between 1/10 and 1/100 microns in diameter.
The smallest pigment used in paint is black, and is typically about 1/100th of a micron in diameter.

So, you'd have to add stuff that was large enough to see to get the "glitter paint" effect you're thinking of. If you used normal paint pigments then, for example, as you added more and more red colourant, you'd start with a transluscent slighly reddish paint which would have increased colour density as you added more red pigment until it finally became red paint. I think it would look pinkish, but pink is a mixture of red and white, and you wouldn't have any white pigments in your paint. Against a white background, your paint would go from a light shade of pink to a red colour. Against a blue background, it would start off looking blue, then purple, and then red.

Most people aren't even aware that the colours in paint come from tiny coloured particles suspended in the colourants added in the paint tinting machine. That's cuz the subject of paint isn't taught anywhere, so it's very much a "blind leading the blind" situation out there.

Here, if you want to learn more about latex paints:
1. go to Painting information and resources for home interiors and exteriors - Paint Quality Institute
2. click on the "Media Center" link near the top
3. Click on "Publications", then "Continuing Education" then "Continuing Education Supplements"
4. Download and read the two PDF files entitled:
"The Ingredients of Paint and their Impact on Paint Properties" and
"How Colour is Affected by the Ingredients of Paint"

If you read through those two brochures, and ask about anything you don't understand, you'll know more about latex paints than most people working in paint stores, and everyone wearing an orange apron.
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Old 12-04-2009, 06:58 PM  
diyonthefly
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thicker paint has more additives, correct? i don't understand the science why agglomeration would cause the whole paint job to be darker, i.e when applied with more shear force. i can understand that there would be blotches of darker paint, but not a uniform darkness. if that's the case, maybe sometimes it's better to use cheaper paint when doing touch ups so as to match the brownian effect of the old paint. in my case, i applied flat white paint called china white with a sponge. could that have created a lighter effect than say had i used a brush. also what is chalking is that cracking or a powdery looking finish? my finish appeared talc looking or powdery. but that was the very next day. perhaps the paint hadn't dried completley. i understand now that i would have been better off using at least an eggshell or maybe even a satin finish. even though satin is still low in the gloss index, what is the appearance of satin paint? is is shiny? if i wanted a little translucence for a better blend, but not so shiny so as to cause flashing or poor coverup, would eggshell be it? i also, i see that the best way to cover up chipped paint on a door frame where there is a thick old coat of paint, on the fly, is to use a thick paint so you can achieve a deeper coat in just an application or two.

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Old 12-05-2009, 05:54 PM  
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thicker paint has more additives, correct?
I don't know. It may have more extender pigments in it to make it more viscous and dry flatter. Or it may have thickening agents (which are considered an "additive") in it.

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i don't understand the science why agglomeration would cause the whole paint job to be darker, i.e when applied with more shear force. i can understand that there would be blotches of darker paint, but not a uniform darkness.
I don't know what you mean by "agglomeration". I suspect the word you're looking for is "coalescence".

The reason why latex paints darken as they dry is because wet latex paint has it's binder in the form of gazillions of microscopic blobs of clear hard plexiglas. Each of those blobs reflect and refract light just like the water droplets in a cloud do. Your eye sees that scattered light as the colour "white", and this is the reason why snowbanks, clouds, steam and the head on a beer are all white in colour, even though nothing inside any of these things is actually white in colour. The white colour arises entirely because your eye sees scattered light as the colour "white".

Once the latex paint is applied to the wall, then the first thing to happen is that the water evaporates from the wet film. There is a water soluble solvent in the water in a can of latex paint called a "coalescing solvent". As the water evaporates, the plexiglas blobs find themselves surrounded by this coalescing solvent at ever increasing concentration. The coalescing solvent softens the plastic blobs making them very soft and mushy. The very same physics that cause water droplets in a cloud to coalesce to form rain drops then takes over and causes the plexiglas blobs to stick to one another and to all pull together to form a continuous film of solid plasticm with the pigments suspended in it very much like raisins in raisin bread.

It's the formation of that solid plastic film out of those gazillions of microscopic clear particles that stops the scattering of light. It's exactly what happens when snow melts to form liquid water. As the ice/air interfaces disappear, so does the white colour. So, as those plexiglas/air interfaces disappear in the latex paint film, the colour of the paint becomes "less white" or "darker".

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if that's the case, maybe sometimes it's better to use cheaper paint when doing touch ups so as to match the brownian effect of the old paint.
It's important to understand what that Brownian Effect is. Basically, the Brownian Effect is the result of the fact that as particles become smaller and smaller and smaller, they start to act like individual atoms and molecules. If an atom hits a cold surface (where the atoms are moving slowly), it loses some of it's energy to those slow atoms, and slows down itself. Ditto for molecules. The particles of soot in the air from burning candles and smoking are so tiny that they're small enough to be affected by quantum physics, and they lose their energy to cold surfaces and tend to stick to those cold surfaces if they don't have enough energy to bounce off the surface. The result is that you typically see dark lines on exterior walls where the wall studs are, and in worse cases, you see dark spots on those dark lines where the drywall screws are. That's cuz wood has a lower R value than insulation, and steel drywall screws have a lower R value than wood.

You'll get very little of that Brownian effect on interior walls cuz the wall surface is the same temperature as the indoor air. It typically only occurs on exterior walls. So you CAN try and compensate for it by adding some black colourant to your paint, but it's hit and miss as to how much black to add. If you burn a lot of candles or smoke, there's gonna be more soot on your walls. If you don't smoke or burn candles, there'll be less. The way I look at it, is if the prospective tenant cannot live in an apartment where the new paint colour isn't an EXACT match of the old paint colour, that's probably not the kind of person I'd be wanting to rent to anyway. They're going to be expecting perfection in everything and everyone except themselves.

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in my case, i applied flat white paint called china white with a sponge. could that have created a lighter effect than say had i used a brush.
I guess it would depend on how you did it. If you just dunked the sponge in the paint and went at it, you'd probably have an awful lot of air in that sponge, and the air would have probably formed bubbles in the paint. If it were me, I'd probably have wet the sponge and squeezed it out before using it to apply paint. Otherwise I can't think of any reason why applying paint with a sponge would result in a lighter colour than painting with a brush or roller.

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also what is chalking is that cracking or a powdery looking finish? my finish appeared talc looking or powdery. but that was the very next day. perhaps the paint hadn't dried completley.
BINGO! A powdery surface on your paint indicates that the binder resins didn't form a proper film. The "powder" on the surface isn't talc or extender pigments, it's those individual tiny blobs of plexiglas that didn't get soft and mushy enough to deform as much as needed to form a continuous solid film with their neighbors. So, I'm afraid that your latex paint film may be imagined not as a sheet of plexiglas with pigments encased in it, but as a pot of sticky cooked rice with pigments encased in it. The rice grains themselves are clear in colour (cuz they're made of plexiglas), but the white colour arises from all of the air/plexiglas interfaces within the paint film that are reflecting and refracting (or scattering) light.

Chauking can also be caused by the deterioration of a latex paint film from exposure to UV light from the Sun, but if you've got a powdery surface on NEW latex paint, then the problem you're having is that the plexiglas binder resins didn't form a solid film. They made a pot of cooked rice instead, most probably because of the conditions under which you painted. Was it particularily cold or humid that day? Were you painting an exterior wall on a cold day? If you can explain the circumstances under which you painted, I can probably figure out why the paint didn't coalesce properly.

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i understand now that i would have been better off using at least an eggshell or maybe even a satin finish. even though satin is still low in the gloss index
Based on what you just said about the surface of your paint being powdery, then I'm thinking it's not due to the gloss level of the paint being so flat. It may be because your paint didn't dry properly.
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Old 04-15-2010, 01:21 AM  
hadiya
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acrylic is better option than vinyl latex



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