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 11-24-2009, 05:37 PM  
diyonthefly
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Default which is better for indoor touch up acrylic or vinyl latex?

I am covering up some spackling in one spot about 4 cubic inches. the spackling is considerably lighter than the white paint on the wall. i matched the paint color with a sample but i want to get the best result possible. I am going to get a flat latex paint but was wondering which would work better acrylic or vinyl latex. i want to avoid a shiny finish and i may try to dilute the paint to get a better blend. also, since i've never did much painting, i was wondering about using a self-priming paint.



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Old 11-24-2009, 06:23 PM  
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Diyonthefly:

You should be aware that there are primarily two kinds of binder used in latex paints in North America:

1. Polymethyl methacrylate - which is the plastic you probably know better as Plexiglas.

2. Polyvinyl acetate - which is the plastic you probably know better as white wood glue.

So, your question is: Which is better for indoor touch-up, a paint that says that it uses a "100% Acrylic" binder (which will be #1) or one that uses a "Vinyl Acrylic" binder (#2).

The answer is neither.

In order to touch up repairs, what's most important is that the new paint matches the old paint colour as closely as possible. It is the pigments used in the paint which both determine the colour and the colour fastness. Some pigments fade from exposure to UV light from the Sun much faster than others, and so if you want a paint that won't fade, you need to choose a colour that calls only for inorganic pigments in it's tint formula.

What are inorganic pigments? They are the modern day synthetic equivalents of the pulverized coloured rocks that artists like Da Vince have been using for millenia. The modern day inorganic pigment Yox, or Yellow Oxide is the synthetic equivalent of the pigment "Sienna", which is named after the mustard yellow ground and rocks found around the Italian town of Sienna. For centuries, artists would pulverize these rocks into a very fine powder and mix that powder with walnut or poppy seed oil to make a mustard yellow colour paint.

For anything to be 300 million years old, like rocks are, they have to be extremely chemically stable, or they would have decomposed by now. That extreme chemical stability manifests itself in extremely high resistance to fading due to exposure to UV light from the Sun. So, if you use a paint colour that calls for only inorganic pigments in it's tint formula, you will have a paint that fades less than other paints, and therefore retains it's colour better than other paints, and therefore allows you to repair walls more invisibly than other paints.

In this Painting forum, scroll down until you find the thread "Accent Wall in Office". Open that thread and read my post in it. That post will teach you which colourants in the paint tinting machine are the organic pigments and which are the inorganic pigments.

You will find, however, that if you live in a colder climate as I do, then dust and dirt will accumulate on your exterior walls (because of something called "Brownian Motion"), and this will cause the exterior walls to darken with time more than the interior walls. The result is that if you repair an exterior wall, you'll see a slight difference in the paint colour. That difference will be very much less on interior walls where dirt won't collect nearly as much. But, in both cases, the discrepancy will always be less than had you used a paint colour that called for organic pigments in it's tint formula.

From my understanding of paint, in order for a paint to be self priming, it has to have huge rocks in it that are almost large enough to see with the naked eye, just like primers do. If you buy such a paint, it will probably have to be a "FLAT" paint. In order for your repairs to be "invisible", not only does the colour have to match, but the gloss has to match too. The problem with flat paints is that airborne dirt sticks to them more than it does to glossier paints, and so flat paints tend to darken more from this "Brownian Motion" than higher gloss paints. But, you can clean most of that dirt off a flat paint using a Magic Eraser, but never all of it.

In my opinion, it's better to have a glossier paint that will be smoother and easier to clean than a flat paint.

In my own case, I use Pratt & Lambert Accolade Satin in the F4750 tint base with a tint formula of 3 drops of black and 2 1/2 drops of Yellow Oxide per gallon. The black pigment "tones" the paint, giving it much better hide for a nearly white paint. Both pigments are inorganic, so that allows me to touch up nail holes well when tenants vacate.



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Old 11-25-2009, 08:32 PM  
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so what's better for covering up the spackle color, flat or gloss? do paint cans state whether or not they use organic or inorganic? if i want to blend with old paint maybe flat is better because of the brownian effect. i'm not going to have the store mix the pigments i'm just buying a mass produced bucket of paint to do it on the fly. also, if i can't find a self-priming paint, what are the risks of painting over a small patch of spackle without priming it. if you could explain priming that might be helpful too. also would you recommend using a sponge with diluted paint, or a roller or brush. also how many coats should i put on. lot of questions here. but this is like the flight tower giving instructions on landing a plane to a passenger. i've never painted before. thanks for the info.

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Old 11-25-2009, 11:10 PM  
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Quote:
Originally Posted by diyonthefly View Post
so what's better for covering up the spackle color, flat or gloss?
Everything else being equal, flat paint will always hide an underlying colour better than a gloss paint. (Post again if you want to know why.)

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do paint cans state whether or not they use organic or inorganic?
No, when you buy paint, the paint will normally come as a white, pastel, medium, deep or Accent tint base. Those tint bases will dry from clear to white if you don't put any colourants into them. The colourants in the paint tinting machine consists of either organic or inorganic pigments suspended in glycerine. They use glycerine as the carrier fluid because it's equally soluble in both water and mineral spirits, so the same paint tinting machine can be used to tint both latex and oil based paints. You can tell from the colour of the tinting colourants in the paint tinting machine whether the pigment in the colourant is organic or inorganic by it's colour.

Quote:
i'm not going to have the store mix the pigments i'm just buying a mass produced bucket of paint to do it on the fly.
The paint store will never mix pigments. They simply add colourants to the paint with the paint tinting machine according to the tint formula of the paint you choose. The reason why the 12 different colourants in the paint tinting machine are different colours is because they each have different pigments in them. Again, you can tell if the colourant you're adding to your paint has an organic or inorganic pigment in it by it's colour. You just take the lid off the colourant in the paint tinting machine, and the colour of the paint tinting colourant is the same as the colour of the pigment that's in it.

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also, if i can't find a self-priming paint, what are the risks of painting over a small patch of spackle without priming it.
It depends on the paint you use over the primer. If you don't prime your spackle or joint compound first, and you're painting with a satin paint, it'll take 3 or 4 coats of paint before the patch without primer looks to be about he same gloss as the rest of the paint. The glossier the paint, the more coats of paint it'll take before the paint doesn't get absorbed into the spackle and dry matte. The flatter the paint you use, the fewer coats of paint it'll take to have the new unprimed area match the rest of the paint in gloss.

[quote] if you could explain priming that might be helpful too. [quote]

There is a difference between a "primer" and a "sealer". A primer is a coating that adheres well to the substrate and improves the adhesion of the top coat. A sealer is a coating that prevents absorbtion and exhudation of a fluid into or out of the substrate.

Basically, a primer is a white paint that has huge rocks in it that are almost large enough to see with the naked eye. It's those rocks, called "extender pigments", that both cause the primer to dry to a matte gloss AND cause the primer to seal the surface of bare drywall or joint compound or spackle. So, most latex primers call themselves a primer/sealer because the extender pigments in it do both jobs.

When you apply a primer over spackle, the spackle tries to wick the primer in by capillary action, but as it does so, the extender pigments plug up the porous surface of the spackle (or drywall) resulting in the remaining primer remaining on the surface of the spackle or drywall. When you then paint with your top coat, none of that top coat is absorbed into the substrate, and you get a uniform gloss level over the entire surface that's painted. If you don't prime, you'll see dull spots wherever paint was applied to bare spackle, bare joint compound or bare drywall.


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also would you recommend using a sponge with diluted paint, or a roller or brush. also how many coats should i put on.
When I repaint apartments the same colour, I simply use a piece of sheet metal to do my "edging". I just put some painter's masking tape on the edge that I bend into a corner and then paint up to that corner with a 3 or 7 inch roller. You don't start with the roller full of paint because then you'll squeeze paint under the sheet metal and get paint on the side of the corner you don't want to get paint on. You start about a foot away from the corner and spread the paint up to the sheet metal so that the roller isn't full when it reaches the sheet metal. That way, no paint will be squeezed under the sheet metal onto the side of the corner you don't want to get paint on.

The best way to tell both the quality of the paint and the number of coats you need is by painting the perimeter of each wall with a piece of sheet metal and a 3 or 7 inch roller, or with a brush. Then, fill in the middle area of the wall with a 7 or 10 inch roller. Allow the paint to dry overnight. If you get any "picture framing", which is a band of increased colour saturation around the perimeter of the room where the two coats of paint overlapped, then you're not getting complete hide in one coat. To judge a paint's quality, the higher the gloss level of paint that will still give you complete hide of an underlying colour in one coat, the better the quality of paint you're buying. So, look for a "picture frame" effect on each wall, and once you no longer see the difference between 1 coat and 2 or 2 coats and 3 or 3 coats and 4, then you know that you've completely hidden the underlying colour. Then just apply the same number of coats it took to get rid of the picture framing effect around the perimeter of that wall to ALL of the walls.

If you're changing the wall colour completely, then you'd do well by having your primer tinted toward the new colour. (So, if you're painting a blue wall red, have the primer tinted pink.) That will give you a "head start" in changing the wall colour.


Hope this helps.
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Old 11-25-2009, 11:12 PM  
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Flatter paints hide better than gloss paints simply because they have more extender pigments in them. Even though those extender pigments are transparent, transluscent or white, they scatter light passing through the pigment by reflection and refraction. The result is that an incident light ray will take a much longer path through the paint film than it otherwise would, and more of that light ray will be absorbed by the paint film.

When a paint doesn't completely hide an underlying colour, what's actually happening is that incident light is passing through the paint film to the substrate where some of the frequencies of the incident light are absorbed, and then reflecting off that substrate back to your eye. Because some of the frequencies of light are absorbed by the substrate, the colour you see will be different than the colour of the incident light. Clear, transluscent and white extender pigments in the paint will both scatter and absorb the incident light on it's way into the paint film, and again on it's way out of the paint film, and that reduces the amount of reflected light you see. Thus flatter paints will be more opaque than higher gloss paints.

Also, both oil based and latex paints will have their highest hide when they're still wet. Just in the same way that clear, transluscent and white extender pigments scatter light, the individual plastic binder resins in WET latex paint will scatter light, making wet paint more opaque than dry paint. As a latex paint dries, the individual binder resins fuse together to form a solid film. As that happens, there is a rapid decrease in the number of plastic/water interfaces in the paint that are reflecting and scattering light. Your eye sees scattered light as the colour white, which is why waterfalls, clowds, snow banks and the head on a beer are all white in colour, even though nothing inside any one of these is actually white in colour. So, initially, when you look at wet paint, it is artificially whiter than it's real colour because of the extra scattering of light at the water/plastic interfaces. As the paint dries, the plastic binder particles fuse together to form a solid film, and that results in a rapid reduction in plastic/water interfaces in the paint film, and that results in much less of the colour "white" eminating from the drying paint film, and that's why both latex and oil based paints darken as they dry.

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Old 11-25-2009, 11:13 PM  
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There's a popular misconception out there that the colourants in a paint tinting machine won't dry the way paint will... that paint tinting colourant doesn't dry. This is because the colourants in the paint tinting machine consist of pigments suspended in glycerine. People don't understand that glycerine is an alcohol and DOES evaporate without leaving a residue. So, if you dispense some paint tinting colourant onto a piece of cardboard or something, and leave it to dry for a week or so (or a few hours on the front dashboard of your car on a hot sunny day), the glycerine will evaporate, and what you'll be left with is a very fine coloured powder, which is the pigment itself.

If you ever meet anyone that tells you that paint tinting colourants won't dry, that is proof in itself that they don't know what they're talking about. They're just parroting what they heard from someone else, and that person didn't know squat about paint. Paint tintint colourant is nothing more than very fine coloured particles called "pigments" suspended in glycerine. Once the glycerine evaporates, what you're left with is those very fine coloured particles, called "pigments".

Ya gotta know this stuff to get your DIY armbadge in Paint.

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Old 12-02-2009, 08:14 PM  
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that's quite a wealth of information. However, the results of my touch up seems to contradict the science... which is the latex paint i used lightened up after it dried which left slightly visible spots. I was touching up little smudges and dirt marks, etc with the paint. It was a vinyl-acrylic binder which i guess doesn't mean much anyway in terms of results. i applied it wet and the cover up was perfect. when it dried, it lightened up and created hardly noticeable spots. this could be that the color wasn't a perfect match and when it was wet it was reflecting the old paint. when it hardened, it became opaque and therefore you could only see the new paint. This could be because i applied it straight out of the can. I think if i had diluted it just a little bit with water i would have gotten a better result. or perhaps i could have used a gloss paint. in terms of color matching maybe its best to have a more translucent paint, like gloss even though it doesn't cover up as well. i was worried about flashing so i used flat paint. i thought gloss which bring out the flash more. another thing i think i learned from this is, when using the sample charts, pick a slightly darker color than the old paint due to the brownian effect on the old paint. or it could be that the guy didn't tint the paint too good. maybe i should have gotten eggshell instead of flat paint.

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Old 12-02-2009, 09:36 PM  
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I responded to each section of your post, until I got to the point where you said you were using a flat paint. The flatness of your paint could very well be why it's not quite the right colour. A rough surface will scatter light, and your eye sees that scattered light as the colour "white".

Wait several days for your flat paint to dry completely. Now, wipe it down with a damp sponge. Is the colour exactly right now? If so, the difference is entirely due to the flat gloss you chose. The water from the sponge never changed the colour of the pigments in your paint. The water from the sponge just made the surface of the paint smooth, eliminating most of the scattering of light that happens when the surface is dry.

Just paint over your flat paint with a higher gloss paint of the same colour.

Here's the reply I started to post:

Quote:
Originally Posted by diyonthefly View Post
However, the results of my touch up seems to contradict the science... which is the latex paint i used lightened up after it dried which left slightly visible spots.
What colour was this latex paint?
Latex paints DARKEN as they dry. You're claiming your paint got lighter as it dried? To my understanding, that can't happen. Is it possible that this lightening effect you're seeing might be due to the time of day or lighting conditions at the time you compared the paint?

Quote:
i applied it wet and the cover up was perfect. when it dried, it lightened up and created hardly noticeable spots. this could be that the color wasn't a perfect match and when it was wet it was reflecting the old paint. when it hardened, it became opaque and therefore you could only see the new paint.
No, that's the wrong way around too.
Latex paints are at their most opaque when they're still wet. Remember all those clear or transluscent blobs of plastic (called "resins") in the wet paint that scatter light and cause the wet latex paint to be artificially lighter in colour? By scattering light, those same clear or transluscent resins also make the wet latex paint more opaque. A they coalesce into the solid film (that is, as the latex paint dries) they stop scattering light, and the result is that the latex paint will darken and won't hide an underlying colour as well as when it was wet.

Quote:
This could be because i applied it straight out of the can. I think if i had diluted it just a little bit with water i would have gotten a better result.
No. Any thinner you add to paint, whether it be water in latex paint or mineral spirits in oil based paint will evaporate from the drying paint completely. So, the end product will be exactly the same whether you had diluted it with a bit of water or not. The additional water would have just resulted in the paint taking longer to dry to exactly the same colour as you have.


Quote:
or perhaps i could have used a gloss paint. in terms of color matching maybe its best to have a more translucent paint, like gloss even though it doesn't cover up as well. i was worried about flashing so i used flat paint.
BINGO!
Wait several days for your existing flat paint to dry completely. Now, wipe it with a damp sponge. Does the colour now match? If so, then the reason why your paint is lighter now that it's dry is because the rough surface of your flat paint is scattering incident light, and your eye sees that scattered light as the colour "white". By wetting the surface, most of incident light enters the paint film and is absorbed rather than reflected as it was off the dry surface. So, you're paint colour is fine. The problem is you have too much white light added by the rough surface of your paint. (if that makes sense)



Quote:
I thought gloss which bring out the flash more. another thing i think i learned from this is, when using the sample charts, pick a slightly darker color than the old paint due to the brownian effect on the old paint. or it could be that the guy didn't tint the paint too good. maybe i should have gotten eggshell instead of flat paint.
Tinting is the most important factor. Even paint companies recommend that if you buy your paint in gallons you should box together all the paint (that is, mix it all together) and pour it back into the gallons to eliminate colour differences between different gallons.

What you should do is take a gloss swatch (one that shows the different gloss levels of the company's paints) and wipe each one with a damp paper towel. Pick the lowest gloss that doesn't change colour when damp.
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Old 12-03-2009, 06:44 PM  
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i think i have it now. what i thought i would accomplish by diluting the paint, is really using a gloss paint instead of a flat paint. painting is a complex endeavor. i think i learned something. thanks alot. i'm sure when the latex paint dries and darkens, the match will be ok. i was looking at it the next day. here's a question albeit a cliche one "how long do you wait for paint to dry?".

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Old 12-03-2009, 07:12 PM  
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DIYonthefly:

Normally latex paint darkens as it dries. Your case was different because of the scattering of light at the flat surface of the paint.

The way you can tell when a latex paint has completed film formation is when that "freshly painted smell" in the room has dissipated. That freshly painted smell is simply the smell of coalescing solvent (usually a chemical called "Texanol"). When you can smell the coalescing solvent, that means that it's evaporating from the paint, and that's one of the last things that occurs during the latex paint film formation process.

So, if you can smell that solvent, then film formation is nearing completion.

However, it's that Texanol coalescing solvent that softens the binder resins so that they can coalesce to form a solid continuous film. It's only once ALL of the coalescing solvent has evaporated from the paint film that the paint will be a hard as it should be. And, as the evaporation rate of the coalescing solvent diminishes, you may not be able to smell it any more and presume that it's all evaporated. It's best to leave it for a few days after that to ensure the film formation is complete and the paint film is hard.

Also, the colourants in the paint tinting machine contain coloured pigments suspended in glycerine. They use glycerine as the carrier fluid for paint tinting colourants because it's soluble in both water and mineral spirits, so the same paint tinting colourants can be used to tint both oil based and latex paints. That means a small hardware store can use the same paint tinting machine to tint all of the paint it sells. Glycerine is much slower to evaporate than water, and it can take up to a whole month for all the glycerine added when tinting paint to completely evaporate from the paint film.
In most cases, the amount of glycerine added will be small because the amount of colourant added to tint the paint to the desired colour is small. Off-white wall paints will start with a white tint base and the amount of colourant added to make it off-white won't be more than an ounce. However, if you want a red, blue or green paint, then they'll start with a "deep" or "accent" tint base that would otherwise dry colourless and clear or transluscent and add lots and lots and lots of colourant to make the paint dry to the colour you want. In that case they have to add an awful lot of colourant, and therefore a lot of glycerine, and in those cases it can take a whole month for all the glycerine to evaporate from the paint film.



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