05 October 2011

Paint, Paint, Glorious Paint!

The SumPod is painted.  Pictures will be posted later.  For the intended colour scheme of brilliant white, it was necessary to use a lot or primer.  A total of five coats over three days.  I recommend that everyone get fast drying primer and plenty of it, because you never know when it's going to rain, get windy, the light vanishes quicker than expected, you run out of paint or the inevitable and unforeseeable demands from family.  Save yourself the hassle, learn from my mistakes and avoid the pain in the posterior that is carrying wet painted parts through the house and the associated complaints about the smell.

As for specific quantities of paint, I was amazed at how much the edges of MDF sucked up paint - it just vanishes.  I used over a litre of primer, far more than I had originally anticipated.   Understandably I knew that a white colour scheme would require the thickest of bases to obliterate the colour of the MDF, but with no previous experience of spray painting MDF, I was surprised and ran out of paint on more than one occasion.  A darker colour would obviously require fewer coats, so you may only need two spray cans for your SumPod.

Get some sand or glass paper, three or four sheets should be enough.  I used coarser grit than the recommended 220, but even 120 grit provides a smooth if slightly scored finish between coats.  The trickiest part was smoothing the curves of the main body as the glasspaper had a tendancy to remove the paint from these surfaces first.  This was compounded by the amazing paint sucking abilities of MDF and goes some way to explaining why my SumPod required so many base coats.

I think the use of spray paint compared to applying the paint with a brush or roller helps improve the surface finish.  That's not to say brushing on the primer would not provide as good a finish, because it is only an undercoat, but I found that spray paint was very easy to use, provides good coverage, makes painting difficult to reach and complex areas (there are quite a few) pretty painless.  Overall I think the extra expense for the speed and ease of use to be worth the extra money.

I'll let you know when I finish the final coat (yes, I ran out of paint, again) if the coarser grit produces a smooth enough finish.  After all I don't need the SumPod to have the glass like finish of a coffin, it's a 3D printer.  The finish should look nice and the paint will afford the SumPod a degree of protection from grubby finger prints (perhaps white wasn't the best choice of colour), oil, splashes of stuff, moisture, small children and that most caustic of substances baby drool.

Until later SumPod Guinea Pig signing off.


  1. Looking forward to seeing the finished Sumpod.

    I did some searching and found some go tips at http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesArticle.aspx?id=26508

    The main takeaway was to use solvent based primer to minimize swelling of the MDF and to use drywall compound to seal the porous edges.

    What kind of primer where you using?

  2. Good find. I didn't specify in the post the type of paint used - Plastikote Super Primer.
    It's a solvent based primer to minimise MDF swelling as you rightly said.

    That's a good tip about drywall compound, worth a try if you already had some, but otherwise for a SumPod the cost of getting some compound exceeds the cost of the extra paint. Unless of course you have some wall cracks that require patching...

    Safety Data Sheet for the primer can be found at:

  3. Fixer: hey, thanks for your work in setting this blog up. I found that on a test piece of MDF I have here, spar urethane in a spray can seals the smooth side in one coat. You have to let it cure for a day or so. Then an enamel Krylon spray did an excellent job for a color coat. The Sumpod might not use the same grade of MDF -- my test piece had a very smooth and almost glossy surface.