Sunday
Nov292009

Prep for Paint

Painting a project like this is one thing, painting it so it looks like it came out of a factory is another. Especially when the cabinet is already mostly assembled.

Choosing a Finish

For this project I hope to have some aspects in high gloss black enamel (much like the finish you'd expect to see on a car or piano. It's difficult to do without a spray booth but I'm dedicated enough to wetsand my way to a smooth and even finish. I'll discuss more on getting a high gloss finish in a later post.

The interior edges above the playfield will get high gloss. The speaker grill and interior edges of the backbox will also get high gloss and the surrounding outsides such as the back of the cabinet will get a semi-gloss smooth finish also in black. The remaining areas of the cabinet will be covered in art. The interior of the cab will get a basic wall paint (white/ivory) to help see in there.

It's a horrible feeling when you come to finish a project. In essence the bare wood or MDF looks clean and even and then the next few steps feel like you are ruining your project and running backwards. You have to brace yourself for a battle that you know will be worth it in the end - it's time consuming and painful but with patience you'll be so glad that you went through with it.

Filling

When trying to get a piano type finish it is really essential that you begin with a flat surface. Any minor distortion will show up. While you can wetsand gloss paint to a point you really need to eliminate as much work as possible at the start. I use a filling compound as shown, provided it can sand smooth you should be right.

This filler really sands smooth. You can apply it liberally and then sand it back.

You begin by blobbing this over the screw holes and other surface imperfections you may have caused during the build. The factory finish on MDF is really a very good surface for painting so you don't need to fill or cover it, just a good MDF primer paint will suffice. In fact this is where MDF has benefits over using plywood which has wood grain that needs filling.

All screw holes get a blob of filler and smoothed with a scraper. You don't want to try and achieve a perfectly flat fill when the filler is wet because you'll more than likely end up digging the hole you are trying to fill. In fact you don't want to mess about with the filler more than you have to, it will start to go off and you'll be left with a mess. Just remember, sanding is the key here and this stuff sands very quickly and easily.

I also allow a generous width and spread around the area so I can sand it back smooth once it has dried. You want the blob to spread far enough all around the imperfection so that any variance can be hidden when sanded. If you've ever plastered walls or similar it's the same principle.

On the other hand don't apply the filler too thick either, no need to waste it.

When filling it's important that you cover any exposed cuts. You can see in the picture above that I run some filler over the cut edge of the MDF. Make sure you get the corners too. Remember, sanding it back is really easy with a powered sander.

And here is the finished cabinet ready for sanding.

Sanding

The next and obvious step is to wait for this to dry. You really want it to dry well before sanding so follow the instructions carefully. I'd then add another couple of hours on top of this if you can (easy in hindsight to do, but very difficult when you're impatiently in the middle of the build.)

I use a small palm Bosch palm sander with 180 grit pads to remove the excess filler. You want to take your time here and ensure the surface is as even as possible. You can in some instances over sand an area and under sand an area. I took my time to ensure that to the touch there was no distinguishable difference between the filler and non filled areas.

The filler will really sand back fast so you want to keep a steady and flat surface with the sanding pad at all times or you'll just create more imperfections. You want to use broad flat strokes rather than small repetitive ones which can quickly remove too much material and create very subtle surface grooves that really show up when glossed. The large strokes also help blend a larger surface area together which helps reduce any visible difference in surface.

In a lot of cases you will need to repeat the above step to fill any new defects that appear after sanding (suchs as gaps in the filler etc) but I was happy enough with the result to move on. (In hindsight even the smallest defect on the high gloss areas can show up so just spend the little extra time you have here to save you hours of work later).

Priming

The purpose of priming is to give the gloss paint something to adhere too evenly. The MDF primer / sealer I purchased also helps lock in the porous nature of the MDF so that the gloss paint isn't absorbed into the MDF leaving behind an uneven coat. The flat finish on MDF already comes factory sealed but any cuts you introduce require a sealant to prevent paint absorption from happening.

Once happy that all the edges were uniform and that the imperfections were gone and smooth I then wiped down all the surfaces and applied 2 thin coats of MDF primer paint with a foam roller. The priming paint dries very rapidly so I could reapply a coat within a couple of hours. You can lightly sand in-between coats with a high grit sand paper. I hand smoothed the final coat off with a 320 grit (wetdry - but dry) paper I had available. You need to take your time here to get rid off all the nibs and dust and imperfections left in the primer, but not so much that you sand so vigorously and remove the primer altogether. The idea is to just remove enough to regain a smooth finish to the touch.

The back door gaps are gone and now looks like one piece of furniture.

All those imperfections are now gone to the naked eye. A pleasing sight after the uglyness of the filler.

Ready for Paint

You may notice that there are a couple of screw holes left exposed on the sides up top ready for the playfield backing plate. These will be filled later when I complete the construction. The area will be covered with vinyl art (not painted) so it's not important that they are filled now.

I should mention that the backbox also got the same treatment as discussed above. However the backbox is now a couple of steps ahead of this as I began its paint process while building the main cabinet. Time is sparce in the world of parenting so you do as much as you can.

High gloss painting is truely a time consuming process to get correct. You don't want to rush it. With a good foundation as described above it will only make things easier. I'm sure others have opinions on how to prepare a surface that is different to this, but so far this is working well for me.

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Reader Comments (3)

I have read with great interest. And your project is looking great. Thank you for blogging all the steps, as I will some day want to follow your example..

December 13, 2009 | Unregistered CommenterPaul

Cool, if you do end up building one - send me some photos. Also make sure you join the hyperspin-fe.com community for more support.

December 16, 2009 | Registered CommenterDan Potter

Hey Dan, just wanted to say thanks for your blog.
I'm about to embark on a Vpinball cabinet myself and it was great reading.

Good luck with the remainder of the build. I'll be checking in :)

February 22, 2010 | Unregistered CommenterKnievel
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