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Author Topic: MDF -. Does it Need Primer?  (Read 4621 times)

Offline obsidian3d

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Re: MDF -. Does it Need Primer?
« Reply #15 on: October 19, 2015, 06:47:04 PM »
Wow I'm working my way through a western town right now and I would LOVE to hear some tips on how you get such a great look Michi!
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Offline Argonor

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Re: MDF -. Does it Need Primer?
« Reply #16 on: October 19, 2015, 07:54:47 PM »
Are we talking MDF or HDF? Makes a big difference. The HDF stuff soaks way less paint than MDF. Even then, I always prime the stuff.

Says MDF on the tin.
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Offline bishop odo

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Re: MDF -. Does it Need Primer?
« Reply #17 on: October 20, 2015, 04:15:53 PM »
MDF is venerable to moisture, mainly on cut edges should be sealed.  What happens is the edge raises just a little making a almost bur that has to be sanded or not.  Once you paint it or prime it that seals it, and that's the most important part, but it seems to me, that after spending the money on all that laser cut goodness, trying to save pennies on the primer steps is a little foolish. 

Offline Argonor

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Re: MDF -. Does it Need Primer?
« Reply #18 on: October 20, 2015, 06:59:32 PM »
Not trying to save money, just not wanting to obscure detail with a perhaps unnecessary layer of paint.

One of my friends told me that his alternate gaming group (Infinity) primed their futuristic mdf with an airbrush, and that the paint seemed to stay out of the fine laser-cut lines - maybe that would also happen with a spray?

Offline Malebolgia

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Re: MDF -. Does it Need Primer?
« Reply #19 on: October 20, 2015, 07:22:59 PM »
« Last Edit: October 20, 2015, 07:28:36 PM by Malebolgia »
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Offline Argonor

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Re: MDF -. Does it Need Primer?
« Reply #20 on: October 20, 2015, 08:07:14 PM »
MDF drinks up paint like a sponge. I have "primed" my MDF buildings with hairspray as it is very much cheaper than spray paint.  And then painted with watered down paint.

I think I may try that approach - in the summer half of the year I am playing games i n the garage attic, and the air can become a bit humid up there, as it is not insulated, and outside air has some access.

Offline Michi

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Re: MDF -. Does it Need Primer?
« Reply #21 on: October 20, 2015, 09:39:52 PM »
Wow I'm working my way through a western town right now and I would LOVE to hear some tips on how you get such a great look Michi!

It´s rather dry and thick acrylic paint slapped on the bare MDF with rough brush strokes in three layers of increasingly lighter tones and a black wash followed by a leather brown wash applied after drying.

Offline Major_Gilbear

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Re: MDF -. Does it Need Primer?
« Reply #22 on: October 21, 2015, 08:31:19 AM »
HDF/MDF + Moisture = bad.

If you use a hairspray to seal the stuff before painting, just be sure that the finished product isn't kept anywhere damp or humid as most hairspray is (for obvious reasons) water-soluble.

I would say that a decent quality spray primer or a decent primer coat laid on with an airbrush is a good idea just to seal the stuff and provide a good surface for the paint to stick to.

I would also avoid using any paints that are very wet directly onto the bare MDF, as the high moisture content could cause the cut edges to swell.

Whilst I agree that primer is used on models to assist with the adhesion of your paint to them, there are a few of other reasons to consider doing the same for MDF:

1) Automotive spray primers have a lot of solvent in them, and this helps them (and subsequent paint coats) to stick to the model even if the surface is very smooth or has a small amount of grease (maybe from very light handling) on it. You can wash a model to minimise this and improve the primer's adhesion, but you cannot wash MDF! After assembly, it may have some grease from your hands on it (especially if it was a tough build!), and the primer will help to avoid any thin coats of paint from leaving uneven areas.

2) The primer seals porous surfaces, and has a little tooth to encourage even coverage of subsequent paint coats. For MDF, I think these are both good reasons to prime.

3) The primer is pretty tough, and (together with a varnish at the end) will assist in salient parts of the models from getting the paint rubbed or scuffed too easily.

As long as you use thin coats (even multiple thin coats will a full period of drying between coats), I would argue that there are more (albeit somewhat marginal) benefits to using a primer than not using one.

Personally, I prime everything regardless. :)
« Last Edit: October 21, 2015, 08:33:07 AM by Major_Gilbear »

Offline Connectamabob

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Re: MDF -. Does it Need Primer?
« Reply #23 on: October 25, 2015, 01:41:32 AM »
One of my friends told me that his alternate gaming group (Infinity) primed their futuristic mdf with an airbrush, and that the paint seemed to stay out of the fine laser-cut lines - maybe that would also happen with a spray?

A major benefit of using an airbrush is you get a much finer and more controllable spray than with a rattlecan. A big reason why I started ABing (and the biggest reason I'd recommend one to gaming modelers) is because it eliminates common rattlecan issues like the sandy texture you see so often in close-up pics, or not being able to hit crevices without overgobbing the high points.

Rattlecan will get you primed enough for paint adhesion, but to get a full sealing coat inside the crevices without going too thick on the surrounding highs/flats will be more of a challenge.

However, if your friend is saying that the AB wasn't getting paint inside the engraved lines at all, as opposed to not overfilling them, then they aren't using the AB correctly. Probably just spraying it in big general passes like you would with a rattlecan. That'll get you a nice coat without texturing, but it won't put paint in crevices any better than a rattlecan would. Should be obvious why. What an AB lets you do is drop paint volume and get in close so you can target the spray right into the engraved lines without overspraying the rest. If they aren't doing that, then they're being lazy, not honest.
« Last Edit: October 25, 2015, 01:44:03 AM by Connectamabob »
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Offline The_Beast

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Re: MDF -. Does it Need Primer?
« Reply #24 on: October 26, 2015, 06:18:19 PM »
Remember, you prime objects to give paint a ground to stick to. The texture and porousness of MDF already act as sufficient ground for painting, so you don't need to prime it.

A major reason for priming, yes.

But, as mentioned, MDF's porousness SOAKS paint in. Is it sufficient to do many very thin coats of base/primer to build up that seal?

'Wet' MDF can lose structural integrity as well; isn't that another reason to try to seal before 'laying it on thick?'

Doug

Offline Eric the Shed

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Re: MDF -. Does it Need Primer?
« Reply #25 on: October 27, 2015, 07:47:18 AM »
you can always seal with pva glue

 

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