Some people have no qualms about tearing into an engine. Others can practically rebuild a transmission in their sleep. Yet, many of these same people are intimidated by doing their own paint job. Maybe it’s the thought of doing inadequate prep work, or the fear of mixing the materials improperly… or just a lack of patience to put in the necessary time. Most likely, though, people just get scared off by bad paint.
Orange peel, wrinkling, paint curtains – these are all conditions that can ruin an automotive paint job. Here is a list of some of the most common paint mishaps and how to avoid them. Included is some basic information on how to fix these conditions.
Bad paint doesn’t have to be permanent. And neither does your fear of painting your own hot rod, car, motorcycle or bakkie. Find out how to avoid (and fix, if necessary) these common paint maladies and tackle your next paint job at home.
Also known as crazing, wrinkling, splitting, or checking, cracking can include cracks of random size and often resembles the wrinkles on a reptile’s skin.
Insufficient surface preparation: Step one in avoiding cracks or many other imperfections is properly preparing the substrate for paint. Cracking or other imperfections in the surface itself should be removed before the new material is applied.
Lifting of substrate: When the wrong reducer is used in a top coat, or when certain materials are top coated before achieving full cure, the undercoat may lift in a way that appears like cracking.
Improper choice in reducer or hardener: Be sure to follow the paint manufacturer’s suggestions on the type of reducers and hardeners to use with each paint. Improper or low quality materials may have an adverse effect on the finished dry paint film.
Incorrect mixing ratio: If too much activator/hardener is used, or if the correct ratio is not properly mixed, defects may appear in the finished dried paint film.
Environmental conditions: Excessive heat or humidity during application and curing can cause surface imperfections such as cracking.
Too much, too quickly: Spraying too much material in full wet coats can lead to cracking.
How to fix it;
You’ll need to allow the paint film to cure completely. Once cured, you can sand out any imperfections and reapply the paint. Avoid the same mistakes by keeping the common causes above in mind.
Runs and Sags – Whether on the side of a vehicle or while repainting a kitchen or bathroom, we’ve all probably dealt with paint sags or runs at some point. When struggling with runs, sags, or curtains on an automobile, there are some likely culprits.
Improper reducer/too much reducer: Again, your choice in reducer and hardener plays a key role in your final finish. Be sure to choose the appropriate reducer for the type of material being sprayed, and the shop conditions in which they will be sprayed. Reducer that evaporates too slowly or excessive use of reducer are two primary causes of runs and sags.
Excessive film thickness: Too much material in full wet coats leads to excess paint that runs.
Insufficient flash time: Not allowing enough time for solvent to flash off of the first coat before applying next coat can also cause runs.
Inadequate air pressure: Paint sags can result from insufficient air pressure at the tip of your paint gun. It’s also important to use the correct fluid tip and air cap, and the proper paint gun for specific materials.
Poor technique: Runs and sags can be caused by improper gun tip position, the speed of the pass, the degree of overlap between passes, and the distance of the gun from the panel.
How to fix it;
If the paint is wet: Remove with solvent, clean the area, and reapply coating. If the paint is dry: Sand out any runs and reapply coating.
Appearing as small, circular craters spread throughout the paint film, fish eyes are a common enough problem so try a specialised Fish Eye Eliminator.
Fish eyes typically (but not always) appear in a paint surface soon after application. There is one reason for the appearance of fish eyes: contamination!
Contamination found on the substrate (oil, water, grease, wax, etc.) is the main cause of fish eyes. Contamination that occurs during the application and/or prep process is the other common cause. This can occur when water and oil enter the air stream due to the absence of a water and oil separator, or the reuse of shop rags, which may have previously been used with silicone or other materials. Paints are extremely susceptible to certain waxes and silicone products, so care should be taken whenever car care products are used in the general vicinity of a paint shop.
How to fix it;
If the paint is wet: Remove with solvent, properly prepare the surface, and reapply paint material. If the paint is dry: Sand out fish eyes, and then reapply paint material. Add a fish eye eliminator to the paint before reapplying. The surface should always be completely clean and dry before applying paint materials.