Whether you are doing a touch-up or a full paint job following the correct methods of mixing your paint will provide accurate repeatable results and a finish you can be proud of.
The main difference between professional paints and the type you get out of a spraycan or touch-up bottle is that it needs to be mixed.
Each paint type and manufacturer selection will have different requirements so it is very important that you get specific information each time you pickup a can.
There are 4 basic types of automotive paint.
The first is Lacquer and this product should not really be used anymore. Yes some manufacturers even big ones are pushing lacquer overall paint kits in your local big box parts suppliers and if you are thinking about painting your car you probably took a look at them.
The colors and cost is not the problem its the life expectancy that you get from lacquer. You can only expect about 3 years max and although that is better then the 6 months that you can get out of a can of spray paint 3 years is really not long enough.
So lets move on to paints you might actually use.
There are three types of enamels you may choose for a restoration full paint job or for a repair.
Synthetic Enamel – very cheap and good for farm equipment
Acrylic Enamel – medium cost good for overall and repairs lasts about 5 years
Urethane Enamel – highest cost best product if you are doing a professional job you want to keep.
For mixing reasons synthetic enamel will come in factory base colors of about 50 choices. Within that group you should be able to find a color that matches your needs but it probably won’t be an exact match of color unless you are lucky to be painting one of the supported colors. Synthetic enamels either come pre-thinned and ready to shoot or you will add a reducer to thin it based on the type of gun you are using.
Acrylic and Urethane Enamels can come either in a factory selection of about 50 colors which will be much cheaper or you can buy a brand name like Dupont, Sherwin Williams, PPG that can be matched to your cars exact color.
Tinting
Not only can colors be matched to the original color they can also be tinted just prior to application to match any fading that may have occurred over time.
Tinting is a serious skill that takes professionals years to learn. There are also other factors that will change your paint color like air pressure, drying time and the number of layers of paint so if you need a perfect job its best to leave it up to a professional.
Mixing the paint for application
Always use a clean container for mixing. Even the slightest amount of oil can ruin your paint job. Purchase an empty gallon can from your paint supply store or get a couple disposable mixing cup for a few dollars.
Use a wooden paint mixing stick and always use a clean one after it has been used to mix paint with hardener in it.
Pour your paint through a disposable filter to remove any metallic clumps or other particles.
Add your hardener at the last moment that way you won’t endup on the phone or chasing the dog while your paint hardens in your gun.
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Like we said about Synthetic Enamels, some Acrylic Enamels may also only require a reducer.
Acrylic Urethanes or what some companies call Straight Urethanes will all require a hardener to help the paint cure. They may also require a reducer to thin the paint.
Mixing Ratios
Each manufacturer and different paint within their offerings will have a set mix ratio.
You will normally mix 4 parts paint to 1 part hardener 1 part reducer.
which ends up being 1 gallon paint(4 quarts): 1 quart hardener : 1 quart reducer
If you need to mix part of the paint to do door jams then you should follow the same ratio.
Reserve 1 quart of paint: 8 ounces of hardener : 8 ounces of reducer
Factory Acrylics such as Kirker paints will come in a 3 quart gallon and require a full quart of hardener to be added. This is a relatively easy system for overall paint jobs but probably not great for repairs. Again if you need to reserve paint for door jams an under hood keep it unmixed at the same ratio.
Pot Life
Pot life is the time after you mix the paint that it will still be sprayable. This can be very different depending on the paint you pic.
Acrylic without hardener can last 8 hours or more.
Urethane will last anywhere from 2 to 4 hours.
Special Spot Job repair paints with hardeners may only last an hour or less.
For this reason you only mix the amount of paint that you can use well within this open window. After this time the paint will begin to harden in your gun and eventually it will gell up and harden so do not leave your gun uncleaned over night.
NEVER pour mixed paint back into your gallon of unmixed paint. Dont even do it if it does not have hardener in it because you will screw up the mix ratio.
Shaking for Metallics
Not only do you need to make sure that your metallics are off the bottom of your can prior to mixing in reducer and hardener you need to continuously mix them in your gun by shaking.
If you buy metalic paint you should use it the same day or have it reshaken. If you can not get it reshaken at your autostore go to any local paint place. If that is not possible then you will need to pour the gallon of paint in a larger container and make sure the metallics are out of the can and suspended evenly throughout the paint by stirring for an extended period BEFORE you add hardener or reducer.
Final Note
ALWAYS read your manufacturers recommendations about mix ratios. Your paint supplier should provide this info and write it on the can for you.
It useto be that all paints had a basic mix ratio you could apply but today each brand and line within that brand has its own mix ratios so make sure you know what you are using and what ratio is correct for your paint.
Never mix more paint then you can shoot in a hour.
Never put mixed paint in your unmixed gallon.