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12 - CLEAR COATING
Achieving a concourse-level clear coat finish is a difficult and demanding process, particularly with carbon fiber parts. There aredozens of variables andpotentialpoints-of-failure along the way. Correctly preparing your part will go a long way towards avoiding potential pit-falls during the clear coating process though, so be sure to read our posts onSurface and Edge Preparation and an upcoming post on spraying primers before you get started. This post outlines the process for spraying a final stage clear coat, but the basic spraying procedure is widely applicable. Check out our posts on plugs, molds, and different finishes to learn more.
TOOLS
- Ventilated Space with Bright Overhead Lights
- Compressed Air
- Spray Gun
- Tweezers
- Rags
- Cleaning Brushes
- Respirator
- Tyvek 1440 Suit
MATERIALS
- Particle Filter
- Clear Coat & Activator
- Degreaser / Cleaner
- Graduated Cup
- Stir Stick
- Acetone
- Latex Gloves
PREPARATION
Before you begin spraying, make sure that yourentirepart is scuffed with 220+ sandpaper,meticulouslyclean and in adust-free space. You’ll needadequateventilation and lots of light fromevery angle to properly see what you are spraying. Don your safety gear and use a rag to wipe your parts down with a de-greasing cleaner. Use compressed air to blow any remainingparticulatesoff of the part. Finally, consider the shape of your part - is it fairly and two dimensional or does it have curvature and three dimensional features? If the latter, you'll may need to go through the following procedure two or three times so that you can spray each surface oriented to avoid runs and pooling. Consider how you will fixture the part in each position before you start spraying. The photo below illustrates a creative solution for spraying a three-sided part in a single session.
SPRAYING
Mix your clear coat,hardener, andactivator ina graduatedcup according to the manufacturer’s directions, stir thoroughly, and pour it throughafilter into your spray gun. Adjust your gun’s air pressure, spray intensity, and spray pattern to an appropriate level. This is highly dependent upon the type of paint you are spraying.
Begin by spraying a light mist-coat across your part. This will allow the following coats to adhere. It should have the appearance of a light speckled “fuzz”. Apply 1-3 additional coats, spraying the material in quick passes across the part until enough material is built up. Be sure to allow the material to dry for a few minutes between coats, according to the manufacturer’s directions. Use this time to examine the surface for debris also known as ‘inclusions’ – if you find an inclusion, carefully remove it with tweezers.
Spraying clear coat is a delicate operation. Too little material will cause dimples and pinholes in the finish, while too much material will causesagsand runs. If you haven’t done it before it will probably take a couple of spray sessions to get the hang of it, so be patient! It can also help to take notes after each session to record what worked and what didn’t – a methodical approach to developing your technique will result in better parts in less time!
When you’re finished spraying, immediately disassemble and thoroughly clean the gun using acetone and bottle brushes. If there is significant build up you can soak any metal components in a sealed container filled with acetone. It is not recommended to soak plastic and rubber components as they will dissolve.
