What Automotive Primer Should I Use Over Old Paint

Thanks to the availability of Internet information, anyone who has ever sprayed a coat of paint can mail their expertise online. This has led to a lot of bad or outdated information. People toss around terms like primer, sealer, 2-part paint, tri-glaze, lacquer, single-phase, and it can get confusing.

Let's start by dispelling 1 of the most mutual misconceptions. Many clients ask their painters to apply lacquer. They think they volition go a better pigment job by using lacquer. This is not truthful. E'er meet a classic car with a pigment surface covered in tiny cracks? That's because information technology was painted with lacquer. Unless you're painting a 100-point concours restoration, you shouldn't be using lacquer. Mod paint is easier to apply, looks improve, and is much more durable that any lacquer paintjob.

How Paint Works

It's critical to empathise how paint works, also as knowing the unlike kinds of paint. New-engineering paint works differently than one-time lacquer. Lacquer was made with very strong solvents. While this allowed solvents to achieve deep into the surface to grade a strong chemical bond, information technology also created a variety of serious problems like crazing and wrinkling. This meant when something when wrong, y'all had to remove all the pigment right down to the metal.

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This is a very simplified drawing, but information technology's an piece of cake-to-understand explanation of how modernistic-technology paint works. The paint is sprayed onto a sanded surface, and the sanded surface provides "teeth" to aid the pigment stick. The solvents in the paint, carry the pigments and resins to the surface, then every bit they evaporate out, the layers bond together.

While urethane paints accept a slight chemical bond, they really need "teeth" or sanded/scuffed surface to hold on to. This is why it is very of import to sympathise the product you are using and what information technology needs. First, you lot need to know how to prepare the surface. What grit of paper do you need to use? How long can the production sit until it needs to exist sanded before painting over it? This is called the "window." All of this information can be found in the production'south tech sheet.

The Paint Windows

There are 2 pigment "windows" that affect the outcome: The recoat window between coats of paint, and the recoat window before painting another round. So, what is a "circular" and how is it dissimilar from a "coat" of pigment? Say you've done the bodywork and are set for primer. Y'all spray three coats of primer — waiting the recommended fourth dimension betwixt each coat before spraying the adjacent coat. These three coats are one round.

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Here's function of my library of tech sheets. A tech or P canvass explains everything y'all need to know most the production. What it can be sprayed over and how to prepare the surface, the kind of spray gun that should be used, the air pressure needed, how the glaze should be applied, recommended number of coats, fourth dimension betwixt coats, recoat windows, and dry times. You'll also learn how it should be mixed and what should be mixed with it. You should have a tech or product canvas for every paint production being used. Read through the sail and follow what it says.

Then, the primer cures overnight. This is the window between rounds. And then, the primer is sanded and one coat of sealer is applied. The tech sheet for the sealer says it needs to dry for 30 minutes (another recoat window), and so one circular of three coats of basecoat-color can be sprayed. The basecoat dries for i hr (recoat window), and two coats of urethane clearcoat is sprayed.

The tech canvas volition tell you the recoat windows for the product. Many pigment problems happen when the recoat window or window rules are not followed. Remember, movie thickness tin can also affect the recoat window. The thicker or heavier the coat, the longer it takes for the solvents to gas out.

Avoiding Delamination and Adhesion Problems

Follow the recoat rules on the tech sheet. If you lot become past the recommended time for recoat, take the time to sand or scuff that surface! Here'south what volition happen if you crook by just a small amount of time. If you're doing a one-color pigment chore, certain the paint will look dandy —at first. So over time, you lot'll detect the pigment might bit easily, or bubbling might form nether the surface, every bit the pinnacle coats brainstorm to lift.

Only, if you're doing any kind of two-tone or artwork, yous'll notice the problems right abroad! Chances are, when you lot're removing any tape, the pigment volition come upward with the record. Ever pigment by the rules of the tech sheet, no affair which production you lot're using.

Nearly paint products are designed to exist sprayed in sure conditions. For example, it's non a good idea to paint when information technology's very common cold or very hot. Standard conditions are temperature, humidity, and air flow under which an automotive paint product's dry time, cure fourth dimension, pot life, and all full general performance characteristics are determined. This information is found on the products tech sheet.

The fifteen-Caste Rule

What happens when you endeavor to paint in colder or warmer temperatures than recommended in the tech sheet? This is where the 15-degree rule comes in. This rule pertains to two-office products, such equally any pigment product with a catalyst or hardener. It explains how temperature can affect a product'southward dry time and pot life when painted in conditions that are hotter or colder than what is recommended in the tech sheet.

For every 15-caste increase in temperature above standard conditions, a product's dry time and pot-life may be reduced past half.
For every 15-caste decrease in temperature below standard conditions, a refinish product'south dry out time and pot-life may be doubled.

Here's a timeline for the average paint job. For example, let's say sealer has been sprayed and basecoat will be applied next. This timeline is based on a lxx-degree store. This is just an example, as all products will be different.

The term pot-life applies to 2K (two-part) products. The pot life is the amount of time a mixed 2K product tin can be used later on the two parts — usually paint and hardener — have been mixed together.

What is VOC?

VOC is one of those terms that gets tossed around and folks don't know exactly what it means. Volatile Organic Chemical compound, or VOC, is a class of materials which include nearly evaporative-solvents used in auto-refinish products. VOC is found in nearly all refinish products. On Sept 11, 1998, a new regulation was put into consequence which regulates the VOC level as practical to refinish products.

Automotive-refinish manufacturers can simply sell undercoats, topcoats, and clearcoats which meet the law. Some states similar California, take enacted VOC regulations that are stricter than the national dominion. Pigment companies take responded by creating water-based paint and solvent products that are VOC compliant. Afterwards in our Painting 101 Series, we'll cover understanding and using waterborne and water-based paints.

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This graphic gives a bones wait at each type of product in a refinish organisation and shows that each one contains VOCs. VOC is measured in pounds of VOC per gallon. VOC information for PPG products can be establish on the product message.

The Undercoats

A paintjob is merely as good as its foundation. Don't apply a inexpensive primer under expensive top coats. And never believe the myth almost using lacquer primers nether acrylic enamel or urethane pigment. Offset your paint job right by picking a paint system and using it through the entire paintjob. Too many things can become wrong with paint, so give yourself an advantage by using products designed to work together.

Epoxy Primers

Recollect of epoxy primer as the foundation for your paint. These primers create a harder, more chemically resistant coating. They're water resistant, have minimal shrinkage, excellent adhesion properties, and volition stick to bare metal, primers, filler, and sometime paint. For example, you can spray epoxy primer onto a surface that's been sanded down to bare metal, repaired with body filler, and then feathered into the original paint. Understand that epoxy primer volition not end or neutralize any rust that has started or is already present. Brand certain to remove and care for whatever corrosion before applying primer.

Refer to the tech sheet for the fourth dimension the epoxy primer can exist recoated before information technology needs to be sanded or scuffed. Missing that window is one of the biggest mistakes painters make. On the other terminate, pay close attention to the time the product must dry before applying pigment over it. With PPG'south DPLV Epoxy Primer, depending on the catalyst used, the product must sit for thirty to 60 minutes when i coat is sprayed. Merely, if two coats are sprayed the expect is 60 to 90 minutes. Yet, when applyingover body filler, the await times are very different — ane hour wait time for one glaze. If spraying two coats, the product must dry overnight before applying over body filler. Wet sanding epoxy primer is normally the best way to prep it because epoxy has a trend to clog newspaper when sanded dry.

Polyester Primers

Polyester primer is a very thick 2-part product and is used when there's a skilful deal of bodywork. Poly primer is great for using over bare fiberglass and epoxy. It's a loftier-solids product and has minimal shrinkage. It sands easily and is perfect for getting those wavy panels straight. Think of it as a sprayable body filler. Using this product tin can relieve hours of time. Get the panels straight with the poly primer, paint one round of urethane primer, sand it, and you'll exist ready to become into sealer and colour!

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Evercoat's Super Build iv:1 is a two-part polyester primer surfacer with great filling capabilities to aid go the surface flat. It's also practiced for belongings downwardly troublesome repairs on fiberglass and SMC plastics.

After spraying the poly primer, block-sand it with 80-grit to flatten the surface. Then practise most of the sanding with 180-dust, and finish with 220. This will provide the flat surface you want. The courser grits piece of work meliorate for getting the surface flat. They carve more effectively, scraping away the high spots. The effectively grits tend to remove less of the loftier spots, passing over the bumps.

Never wet-sand polyester primer! It will blot the moisture and may cause problems downwardly the road if it doesn't completely evaporate before painting. While polyester primers are bully for filling, they can exist porous. One time you're finished sanding the polyester primer, use a urethane primer or a sealer over information technology. Urethane primers are a meliorate surface for basecoats. The urethane primer is much denser and seals the polyester surface. Always bank check the production sheet to know what works best for the poly primer y'all're using.

Primer Surfacers

A quality urethane primer-surfacer will exercise a expert chore of leveling out the transition from plastic filler to metal, equally well equally filling the sanding marks in the filler. But, don't try to apply primer-surfacer where plastic filler or polyester primer can be used. Continue to the recommended number of coats. That information — plus recommended air pressures and wait times — can be found in the product sheets. Each production is unlike, so brand certain to read through the product sail earlier priming. Never leave a two-function primer sitting in the spray gun. Most catalyzed primers offset to harden in about an hour. Allow each glaze flash (dry out dull) before applying the adjacent.

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K36 is a standard-build urethane primer. K38 is a high-build primer. K201 catalyst can be used with either one. They are both groovy quality primers, sand beautifully, and are very easy to use.

Urethane primers come up in a standard and loftier-build variety. Urethane primers also have great filling qualities. Follow the instructions for mixing and flash times (dry out times in between coats). Primer surfacers shrink when flash times (usually 5 to ten mins) are ignored. Practise non use a hardener meant for ane product with a unlike product.

If preparing the surface for sealer and topcoat awarding, employ 320-grit when block-sanding urethane primer-surfacer. It's rough enough to sand it quickly and flatten out whatever small imperfections. Then, moisture-sand the surface with 400-grit. You tin can also outset by wet sanding with 400-grit wrapped effectually a Durablock, or whatever block you feel will work best for the surface. Spraying a lite guide-coat on the surface prior to sanding shows the high and low areas, and helps keep the body lines straight equally yous sand.

Sealers

Years ago, I never used sealer. At present, I don't even consider painting without start spraying sealer. Recollect of sealer as an insurance policy. Sealer takes care of many problems. It creates a bond betwixt properly sanded primer and the basecoat pigment. Sealers help the paint to stick, and tin can reduce the take a chance of having the topcoat paint run. Sealer fills those light sand scratches and can diminish very slight imperfections. The sealer too helps to "seal" the surface. The edges of the layers that were sanded-through tend to heal under a coat of sealer. If sealer was non used, they might show up through the topcoat.

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Considering I use PPG's Deltron organization, my favorite sealer is PPG's K36 primer equally a moisture-on-moisture sealer. It's mixed 4:2:ii:one with their DCU2021 Clearcoat, DT Reducer, and DCX61 Goad. I spray one wet coat, wait about thirty minutes, then continue with the basecoats.

Sealers too assistance the basecoat to flow. Only, since sealer isn't sanded, information technology volition leave more texture if it's non sprayed apartment. If you become a grainy surface with the sealer, that surface will show upward in your basecoats. Wait times tin can be critical with sealer. Look as well long, and sanding will be needed in order to assure proper adhesion of the basecoat. Too curt a wait time, and solvents might exist trapped. Sealer adds to the cost of the paint materials, but the troubles it prevents makes it well worth it.

Colored sealers can also exist a large assist. A white sealer under a light basecoat, helps the topcoat to have better coverage. Some sealers come in a range of colors, then check your paint brand for its sealer choices. PPG'due south Deltron V-Seal DAS302 Sealers are offered in white, light gray, and nighttime gray. At that place are some sealers than tin be custom tinted to better match the topcoat color.

An Easy Manner To Avoid Many Painting Problems

When using 2K products, the best way to avert bug is to only apply the hardener or catalyst designed to go with that production. Information technology doesn't matter if your buddy tells you, "Certain use that, I practise information technology all the time." You take a chance when using a hardener that goes with a unlike brand of paint or filler. Chances are, something is going to go very incorrect, and you will never know the real cause of the problem. If you lot practice not have the correct hardener to go with the stuff yous're using — due southsuperlative, and wait until you lot go the right hardener. Information technology'due south never worth information technology to use questionable hardener!

Next time, nosotros'll take a shut look at basecoats, and teach all you ever wanted to know about solid colors, metallics, candy, flake, and pearls. What is candy colour and why does it need a base? The all-time mode to get that pearl color to glow. Why are black and white two of the hardest colors to properly spray? What is the trick to spraying a chip paintjob with minimal coats? And there will be some sweet processed paint photos to drool over. Agreement how paint works is the key to getting that perfect paintjob!