America - Auto Painting

The automotive painting tips presented here are an accumulation of approximately 55 years of experience, when myself and other young hot rod enthusiast friends were painting and customizing our hot rods and cars (American Graffiti Days 50’s, 60’s & present). These painting tips are provided so you can avoid the mistakes we made and the skills we learned, including many skills we learned from professional automotive painters, many of which will save you time, money, and heartaches.

Preparation Before Painting (Absolute Cleanliness)

1. Initially wash the entire vehicle first with Dawn or Joy detergent and water, it’s the best for removing contaminates like wax and silicones, dry with clean towels.

2. Rubbing alcohol safe to use on car paint.

Car paint can be cleaned effectively by rubbing alcohol, which removes grease, oil, and heavy soil. Mix Ratio: 50% Alcohol 50% Water.

3. Before painting a metal item, wipe the surface with a solution with 1 part vinegar to 5 parts water. This cleans the surface and makes peeling less likely. The acidic qualities of the vinegar will clean and degrease the metal surface and help the paint adhere.

Clean any and all primed, filled surfaces (like Bondo), or painted surfaces before applying Clearcoat. Use micro fiber, or tack cloths, spray the solution with one hand and wipe with the other hand. Single stage: all you need to do is tack the entire vehicle once before your paint job and never between your coats.

Special Note: If you’re going to be spraying plastic surfaces or fiberglass surfaces, you should, after basic cleaning preparation, spray these surfaces with “ADHESION PROMOTER.”

You should always clean any surface you plan to paint, including metal. Any oil or dust left on the surface will prevent the paint from sticking. You can also use acetone, or Klean Strip Prep-All to wipe down the surface before you paint.

Automotive commercial cleaners are expensive; the household cleaners discussed above are just as effective. If you don’t have any of these cleaners available, you can use Windex. DON’T TOUCH ANY SURFACE TO BE PAINTED WITH YOUR HANDS OR FINGERS, use rubber gloves, the oils from your body will prevent the paint from bonding properly.

SCOTCH BRITE GRIT CHART (Scuffing)

3M Scotch Brite Nylon Pads:

7445 - White pad, called Light Duty Cleansing - (1000) 1200-1500 grit

7448 - Light Grey, called Ultra Fine Hand - (600-800) 800 grit.

6448 - Green (?), called Light Duty Hand Pad - (600) 600 grit

7447 - Maroon pad, called General Purpose Hand - (320-400) 320 grit

6444 - Brown pad, called Extra Duty Hand - (280-320) 240 grit

7446 - Dark Grey pad, called Blending Pad (180-220) 150 grit

7440 - Tan pad, called Heavy Duty Hand Pad - (120-150) 60(?)

Blue Scotch-Brite is considered to be about 1000 grit.

Note: Self-etching primer is really nice to work with. It dries fast, and tough. Primers take between one and four hours to dry on average. However, the exact drying time depends on the primer type, room temperature, humidity, and the surface you're painting. Most manufacturers advise waiting at least 60 minutes before painting over primer.

Remember: You must spray a coat of surfacer/primer/sealer over self-etching primer before spraying a base coat or single stage acrylic/urethane coat over it.

Personal Note: Based On my experience, before spraying any Acrylic/Urethane base coat or single stage paint over primer it’s better that you let any applied primer to cure for at least 48 hours. If you fail to do this you could or may experience an adverse reaction to the applied primer, base coat, or single stage paint.

Acrylic Enamel & Urethane Paint Compatibility

You can spray single stage acrylic enamel over single stage urethane paint, or vise versa. It’s always best to scuff the surface to be painted and wet sand it with 400 - 600 grit, you can also prime it with a surfacer/sealer to insure a perfect bond. Urethane adds durability to the finish.

Spraying Clearcoat Over Single Stage Paint

Can you spray clearcoat over single stage paint, the answer is YES. Actually spraying urethane clearcoat over single stage paint whether urethane or enamel single stage will make the paint even more durable. However, the caveat is that you have an approximate 18 hour window to accomplish this after spraying the single stage paint, or base coat.

Single Stage Acrylic Enamel/Urethane Paint Systems

Base, Clear-Coat Or Primer

Single-Stage High Gloss Paint Coating Systems are Designed for Overall Automotive Refinishing. It’s an easy to spray fast-drying topcoat system that provides a long-lasting and very high gloss finish result. It’s a very durable, chemical and solvent resistant coating that also resists chipping, cracking, and UV ray fading.

Single Stage Paint Has A 8 to 1 mixing ratio, 8 parts Paint Color to 1 part Wet Look Acrylic Hardener.

Single stage paint is a 2.8 VOC when used as packaged, as no reducer is required (optional reducer sold separately). The optional additional reducer may be added at a rate of up to 1 quart per gallon (25%) if desired. Use XR Series Exempt Reducers to maintain a 2.8 VOC Level or use the UR Series Urethane Reducers for a 3.5 VOC Level.

Optional Reducers Are Available Separately

My personal recommendation is that you should always use/add reducer to the paint. Let me explain.

Depending on the climate temperature and humidity in which you will be spraying the paint, it will have an impact on how the paint will flow out and prevent adverse reactions like orange peel.

There are three reducers available for climate:

Fast: 60 – 70 degrees

Medium: 70 – 85 degrees

Slow: 85 degrees and above

Many professionals prefer slow reducer above 80 degrees.

Primers are typically 3:1 or 4:1 ratios, single stage paint is generally an 8:1 ratio, which means they consist of only the paint or primer, hardener is an additive, but NO REDUCER. Caution: I always add reducer based on the temperature in which you will be spraying/applying the primer, single stage paint, or clear coat. In temperatures up to 70 -85 degrees use a mid temp reducer, in temperatures 85 and above use a slow reducer. It’s wise to do this because the paint will flow better, will help prevent orange peel, and help prevent other adverse reactions.

So I recommend mixing ratios of 3:1:1 or 4:1:1 depending on the primer product you’re using, and if using a single stage paint with a 8:1 ratio change that to 8:1:1 and add reducer. All Acrylic Enamel/Urethane paints and primers require hardener.

Example: The first part is paint, the second part is reducer, and the third part is hardener. Example: Based on a total volume of 8oz of mixed product you need for the job, and the manufacturers specified paint ratio of 8:1:1, this would = 5.33 oz paint, 1.33 oz of reducer, 1.33 oz of hardener.

Paint = Single Stage Paint – Base Paint Color – Clear-Coat.

Additives = Reducer & Hardener.

Explanation Of Mixing Ratios

You have total parts that together which equal total ounces. Divide total ounces by total parts to find out how big each 1 part is.

Example: 20 Total Ounces & 11 Total Parts

Each part is 1.81819 oz (rounded off) so

8 x 1.81819 of part 1 = 14.54552 oz.

1 x 1.81819 = 1.81819 oz.

2 x 1.81819 = 3.63638 oz.

Restoration Shop Acrylic Enamel Some Mix Ratios

Prep: Primer & Sealer – Mix Ratio: 3:1:1 (Primer, Hardener, Reducer), Primer Pot Life: 2 - Hours

Mixing Ratio Paint: 8:1 (Color, Hardener, No Reducer)

1 Part AE3001 Wetlook Mid Hardener (Slow, Mid, Fast)

2 Parts Urethane Reducer (Slow, Mid, Fast)

Pot Life: 8 Hours

Drying Time Between Coats: 10 – 15 Minutes @ 70 Degrees

Required Coats: 2 – 3 Coats

Dust Free: 40 50 Minutes

Tack Free: 3 Hours

Spraying Rustoleum Oil Based Enamel

What Reducer/Hardener To Use

Reducer Is Basically A Paint Thinner

Mix Ratio: 4:3:1 (Average)

The best way to thin Rustoleum oil-based paint for spraying is to mix 6.5 ounces of acetone for every gallon of paint.

Mineral Spirits = Slower Dry Time 80 Degrees & Above.

Acetone = Faster Dry Time Below 80 Degrees.

Hardener/Catalyst: Any Hardener Will Work (Slow, Mid, Fast).

Substitute Paint Reducers & Hardeners

In a word, “NO”, don’t use substitutes for paint reducers and hardeners. Paint is based on chemistry, not all paints are created equal. DO NOT SUBSTITUTE ACETONE OR PAINT THINNER for automotive paint reducers and hardeners. YES, lot’s of individuals say you can do this, but most of this is ill advised, it’s best to error on the side of caution.

YES, automotive paint reducers and hardeners do contain some acetone, but the entire physical chemistry of automotive paint is made up of other components/chemicals to off to offset the harsh effects of using acetone only as a paint reducer. Using straight acetone as an automotive paint reducer is not advisable, it can in some cases cause damage to the paint and cause it to lift, or result in other harsh affects damaging your paint job, either now or later. Use recommended paint reducers and hardeners, YES, they are more expensive, but you won’t risk damaging your paint job. The same applies to using straight paint thinner.

Note: If spraying Rustoleum oil based Enamel, you may use acetone, or paint thinner as prescribed by the manufacturer’s directions. Remember, the chemistry of automotive acrylic enamel/urethane paint and Rustoleum oil based enamels are different in their chemistry, use what the paint manufacturer recommends.

Spraying

HVLP Spray Guns (General)

Use 28-29 PSI for clear coat and 26-27 PSI for base coat

, use 25 PSI for primer.

NOTE: If in a very humid climate it’s advisable to keep the compressor drain slightly open to keep water from entering the line. Be absolutely sure to install a quality filter drier unit at the output of the compressor output and a filter at the inlet of the spray gun.

LVLP Spray Guns (General)

Recommended LVLP Low Volume Low Pressure Spray Gun Settings for (LVLP) spray gun 26-27 psi for base and clear coat, primers are a little lower at 25 psi. You can spray a vehicle using a 21 – 25 gallon compressor. Hold spray gun 6 – 12 inches from surface with steady motion from side to side (distance is also determined on type of primer, base coat, clearcoat, and whether applying a tack coat, medium coat, wet coat, or mist coat).

NOTE: If in a humid climate it’s advisable to keep the compressor drain just cracked open to keep water from entering the air line. Be absolutely sure to install a quality filter drier unit at the output of the compressor output and a filter at the inlet of the spray gun.

Paint Overlap & Wet Edge

When spraying a basecoat or clearcoat it’s best to never go below a 50% overlap, I recommend a 70% overlap to keep a wet edge and prevent dry spots or striping. Obviously there are circumstances that require changes in paint application such as touchup, but as normal practice when doing a paint job 50% - 70% overlap is pretty much the rule of thumb.

Recommended Average Spray Gun Nozzle Size:

1.4 All Around Tip – clears, base coat, single stage paints.

1.8 For Primer - will apply primer quickly.

Approximate Amount of Paint Required For Painting

When painting an averaged sized car, a one gallon kit (of enamel/Urethane paint) is usually just enough for a medium sized sedan car or light truck.

We always suggest to mix up a small batch of paint or clear coat and spray a test panel before you go at your project. Make sure you dial in your settings, mixture, and technique so you can quickly and efficiently lay your paint or clearcoat. If you have a nice selection of activators you can paint throughout the warm months of the year.

Paint Required – 1 Mist Coat 1 Wet Coat (Paint Only)

Fender = 8 Sq. Ft. – Paint = 5.12 oz

Hood = 20 Sq. Ft. – Paint = 12.8 oz

Roof = 18 Sq. Ft. – Paint = 11.52 oz

Door = 8 Sq. Ft. – Paint = 5.12 oz

Quarter Panel = 14 Sq. Ft. – Paint = 8.96 oz

Tail Gate = 11 Sq. Ft. – Paint = 7.04 oz

Add Reducer .25% & Hardener .25%

Quart = 100 – 120 sq.ft.

Sq. Ft. = .27 oz - .32 oz

Painting Single Stage

1. Priming & Seal Surface

2. Shoot A Tack Coat

3. Shoot One Medium

4. Shoot One Wet Coat

5. Shoot One Mist Coat (Drop Coat)

Note: If you’re going to be spraying plastic surfaces or fiberglass surfaces, you should, after basic cleaning preparation, spray these surfaces with “ADHESION PROMOTER”, then follow with primer/sealer. Do not confuse primer with adhesion promoter, they are two different things and serve different purposes in automotive painting.

Typically, for an entire car or small truck (1/2 – ¾ ton) you should plan on 5 quarts of paint if shooting single stage urethane paint. If you’re shooting base coat and clearcoat, plan on 5 quarts of paint and 5 quarts of clearcoat. Be sure to purchase the required reducers, and hardeners. It’s always better to have extra then not enough to complete the project. Also, any left over paint, clearcoat, reducers, and hardeners will come in handy for any needed touch up or repairs.

· Small Cars – Miata, Minis, Model A roadsters and the like typically take about two quarts of single stage paint to apply enough coats to cover them, plus the reducers and hardeners.

· Medium to Full-Size Cars – Your typical muscle car, modern sedan, or full-size car usually will use most of a gallon of single-stage paint. Usually it is best to buy a gallon kit. If you’re spraying base coat/clear coat, it may only take 2-3 quarts of base coat to cover completely, however, professionals will usually recommend a minimum of one gallon to 5 quarts of single stage, base coat, and clearcoat.

· Trucks and Vans – Obviously, these are bigger and you will need more paint. Buy at least a gallon plus an extra quart of paint for regular sized trucks and two extra quarts for vans, full-sized SUVs and crew cab trucks. Don’t forget, you have to paint inside the bed too. If spraying base coat/clear coat, a gallon of color may be enough but buy more than a gallon of clear.

· Clear Coat – Always buy a full gallon kit of clear and mix as needed. You can always use leftover paint that has not been mixed with activator for spot repairs or small projects.

· Same Color Respray – If you are respraying a typical car the same color because the clearcoat has failed or after collision repair, you will likely only need about two quarts of base coat color. You will still need a gallon of clear, though. I would always recommend a gallon of color paint and gallon of clearcoat, better safe than sorry; you don’t want to run out of paint. Remember, you will also need reducer and hardener.

· Single-Stage vs. Base Coat/Clear Coat – You will use more single-stage paint then you will basecoat to cover any given car. But chances are you will use less total paint when you compare the amount of basecoat and clear coat applied compared to the single-stage paint.

Temperature Range Of Hardeners & Reducers – Activators & Hardeners Are The same Thing

1. Slow Reducer/Activator– Slow activator is great for when you may be painting on a hot summer day when the temps are over 80F. Once you fine tune your mixture you can use this on a hot day and your paint will flow out nice and flat and you’ll have enough time to lay all that you’ve mixed in your gun. Using this activator on too cool of a day would cause the paint to take much longer to flash and can cause imperfections in the paint. If you are in a pinch you could tweak the mix ratio, but do this with care!

2. Medium Reducer/Activator– We formulated this activator to be the best “all-around’ activator when painting. If you are unsure which activator to choose, this one will work in most climates. Just remember that when you reach higher temps around 80F it may flash too quickly (causing “dry” spots) and with the temps under 70F it may take quite a while longer than normal to flash.

3. Fast Reducer/Activator– Spraying on a cool fall afternoon or on a night when the temps are under 70F? Then you need our fast activator! It will speed up the flash time and allow you lay your additional coats of paint or clear coat in a reasonable amount of time in cooler weather. In a pinch you can use our Medium activator as well, but remember it could raise your flash/cure times greatly!

3M Bondo Body Filler & Date Coding

EU1118M1040017

First digit 1= year. It would mean it is made in year 2021.

Next three digits 118= days in the year. Made on 118th day.

Your product was made on the 118th day of 2021. The Bondo(R) Fillers have a 16 month shelf life from that date.

Surface Sealer Vs Epoxy Primer Vs Etching Primer

A primer surfacer/sealer is used to correct minor surface irregularities and to stop your top coats from being absorbed by a more porous substrate. YES, you can spray 2K primer surfacer/sealer over existing acrylic/urethane paint. It also helps to remove/hide imperfections.

Epoxy Primers when used on metal are for corrosion protection and helping with adhesion. It’s a NON-SANDING Primer! The Correct Name Should be "EPOXY SEALER", because that's all it is! This product is a sealer to use on different surfaces for protection from foreign elements to eliminate contamination! But it's not the only primer that you can use for bare metal, it's just one option.

Etch primers are convenient for the priming of all types of metal that require a very quick turn-around time. They only require a very thin coat in order to etch the metal surface and create a tenacious bond. Zinc phosphate pigment offers some degree of corrosion protection. The fast dry characteristics allow the topcoat to be applied shortly after primer application.

Both Epoxy Primer and Self-Etch primer (Self-Etching primer) can be used on bare metal. Both provide corrosion protection, and both can be top-coated with primer surfacer.

If you’re doing some body work and you have some bare metal, you don't want to just put regular primer surfacer because it does not have the corrosion properties like Epoxy or Self-Etch.

So, how do you choose if you use Self-Etch or Epoxy?

It’s really just a preference and depends on a your individual variables. With a restoration shop, they're probably using more epoxy. If they're a high production shop, like a body shop that runs a lot of cars through, they're probably using Self-Etch.

The reasoning behind that, Epoxy is the only primer that you can put body filler on top of. You shouldn't apply body filler on top of a Self-Etch primer or primer surfacer, but with epoxy you can. Our opinion is if you're going to be doing some body work, the best thing is to put Epoxy Primer on top. That way, you seal it all off and prevent it from any rusting, and then you can do your body work.

You can spray self etching primer over body filler, you can apply self etch primer over fully cured filler. As long as you let the primer fully cure and then scuff the surface it will be fine. As a matter of FACT body filler works better when applied over a protective primer (epoxy or self etching) simply because the primer helps protect the bare steel from moisture. Body filler is extremely porous and will absorb moisture just from the air. That moisture can then attack the underlying steel if its not protected with a good quality primer. It would be better to use an epoxy primer but self etching will work fine. It's just yesterday's technology.

Some advantages of Epoxy over Self-Etch:

Epoxy is very friendly (user friendly) and is very compatible with other products. You don't have to worry about anything lifting like you might with a Self-Etch primer. With epoxy, you can lay it over just about anything, body work, sanded paint, metal and you're going to be fine. With Self-Etch, if put it over different layers of paint, if put on too wet, it's going to lift because Self-Etching primer has acid in it. Be aware of this. Epoxy can be more expensive, but then again….when you are already spending hard earned money on restoring the car of your dreams, a few extra bucks isn't going to break the bank.

Some advantages of Self-Etching over an Epoxy:

It's a little bit straighter forward. There are no induction times with Self-Etching primer. There are 1K products that work well for corrosion protection, that are also available in spray cans. So, if you have just a small area and you're wanting to apply such corrosion protection to, a Self-Etching primer in a spray can may be the way to go. Very simple.

There are a lot of ways to do this. If you have a bigger area, let's say bigger than a gold dollar coin, you can mix up some epoxy and use that. If it's smaller than that, you could use a spray can of Self-Etch primer.

The advantages Self Etch over other metal primers are as follows:

1. Provides excellent adhesion over a variety of different metals.

2. Can be applied with minimal preparation (clean, degrease and abrade, refer to data sheets).

3. Rapid cure, allowing over coating with thin film topcoats in substantially less than 1 hour.

4. Zinc phosphate pigmentation offers some degree of inhibitive corrosion protection.

Lastly, there is one third option, and that's a DTM, Direct-to-Metal primer. This is a primer surfacer, so you get your sandability with it. But it also has some acid in it, which acts like a Self-Etching primer. DTM can be applied directly to steel and then sanded just like a primer surface.

Important Notes: On epoxies, some have an induction time. Think of it as they have to kind of get to know each other a little bit before they bond.

Compressors Tricks & Tips

Many DIY spray painters do not have a $1,000 - $2,000 air compressor setup to deliver sufficient air volume to the spray gun (i.e. HVLP Spray Guns & air tools), however, some may have a two smaller compressors like 26 - 30 gallon size compressors equipped with 2Hp - 2.5Hp compressors like those found at Harbor Freight and Walmart, example: Campbell Hausfield 26 - 30 gallon compressors.

Although it’s possible to spray a vehicle with a small air compressor, in general bigger is better. The issue here is that it’s best to have an air compressor that’s capable of delivering sufficient air volume for the spray gun (i.e. HVLP spray Guns & air tools). If by chance you have two smaller air compressors you can join them together by constructing a simple air manifold and joining the output from both compressors to provide sufficient air volume to feed your spray guns, air/moisture filtering, and air tools. Quite often you can find compressors on the “CHEAP”, at yard sales, or in the want ad’s.

Thinning Latex Paint For HVLP Or Wagner Paint Sprayer

In general, thinning latex paint should be done at a minimum of 10% or 1 gallon of paint to quarter cup water. If you are using an HVLP sprayer or handheld system, you might have to increase your water percentage to 20-30%.

What is Floetrol, it’s a latex paint additive used as a conditioner and thinning latex paint.

If you don’t have any water to use, Elmer’s Glue is probably your best option for a Floetrol substitute. You will get the same pouring consistency as Floetrol if you dilute your glue with water. Elmer’s Glue-all (similar to Floetrol) will dry your painting to a matte finish.

Spray Gun Settings For HVLP & LVLP Spray Guns

Ok, there are three settings that are required to properly adjust your spray gun, these are working & static air pressure, fluid, and fan adjustments. These settings are also dependant on the spray gun setup you’re using (obviously).

It’s best to show how this is accomplished in a video. I’m including two excellent videos on this subject.

1. https://www.youtube.com/watch?v=pNfjSFyGYiM

2. https://www.youtube.com/watch?v=joOv4oLKj4U"

Please keep in mind that there are numerous variables for setting up the spray gun, these include, climate (i.e. temperature), spray gun quality, working & static air pressure, fluid, and fan adjustment. The above video will give a pretty good handle on how to make these adjustments; obviously, you’ll develop a feel for the particular spray gun you’re using.

Lastly, be absolutely sure to select the correct paint activator (hardener) and paint reducer for the temperature climate you will be painting in, failure to select the right activators and reducers will result in a failed paint job.

Like anything else, it’s a skill that you learn, this little tutorial should help you get started in the right direction. “REMEMBER, IT’S ONLY PAINT”.

Primer & Paint Mix Ratio

You can spray the primers noted below without reducer, however, it’s generally advisable to add reducer to the mix so the paint will flow out better and prevent orange peel, especially when temperatures are above 80 degrees. Remember that primer is “paint”, not an additive, reducers and hardeners are additives. Single stage paint, base coat, & clear-coat are all “paint”, the first part in the mix ratio, the second part is reducer, the third part is hardener.

Fast – Medium – Slow Reducers & Hardeners

There are three reducers available for climate variations:

Fast: 60 – 70 degrees

Medium: 70 – 85 degrees

Slow: 85 degrees and above

Professionals prefer slow reducer and hardener above 80 degrees, especially in higher humidity. Some trial and error may be necessary to find what works best in your climate with the products you are spraying.

Here are mix ratios for 1 pint of sprayable primer or paint:

1 Pint SpeedKote Primer 4:1:1

Primer: 5.33oz – Slow Reducer: 1.33oz – Hardener: 1.33oz

1 Pint KustomShop Primer 3.1.1

Primer: 4.8oz – Slow Reducer: 1.6oz – Hardener: 1.6oz

1 Pint TCP Single Stage Paint 8:1:1 – Paint: 6.4oz –

Reducer: .8oz – Hardener .8oz

Explanation Of Mixing Ratios

I’m repeating the explanation/examples of how to determine mixing ratios for paint, reducer, and hardener so you have a better understanding of how this is accomplished.

In one of the examples on the previous page you have total ounces of product that equal 8oz (1 pint) made up of paint, reducer, and hardener with a mixing ratio of 4:1:1.

Divide the total ounces (8oz Pint) by the total parts (ratio) which will give you the ounce(s) per part.

Explnation: A ratio of 4:1:1 means that you have 4 parts paint, 1 part reducer and 1 part hardener for a total of 6 parts.

Divide 8oz (1Pint) by 6 total parts, each part then equals 1.333 oz, then multiply 4 x 1.333 which equals 5.333 oz of paint, then mutiply 1 x 1.333 which equals 1.333 oz of reducer, then multiply 1 X 1.333 which equals 1.333 oz of hardener.

5.333 oz + 1.333 oz + 1.333 oz = 7.999 oz.

If you add this all together it equals 8oz (1 pint).

RWK

04/30/2022

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