Need help with Painting MDF

I’m wanting to do some layered work. I can use Stains with my Baltic birch wood, and that works fine for the application.

I bought some MTN 94 paints based some suggestions from Blue Laser Designs Dude… He also mentioned a specific kind of Filler/Primer one can consider to use prior to painting MDF.

I’ve got a piece cut that was primed after cutting, and painted last week and it’s still tacky kind of. It’s been in the house where relative humidity is fine so it’s not that.

How are you all painting this stuff? Prep Work prior to painting? Kind of paints used? etc… Now I have around 20 can’s of this stuff just collecting dust.

Any suggestions would be greatly appreciated.

Are you really using mdf?

That is fiberboard, it’s usually made from ground up debris that’s compressed and glued together.

It’s difficult to cut, makes a mess in the machine and it stinks…

I’d suggest some type of ply or solid wood.

A link to the video or site you referenced would be nice…

:smile_cat:

Hello Mr. J

This is what I bought. I cut’s nicely. Just can’t paint the damn stuff good.

This stuff is like a sponge… it sucks up everything, including water…

Might have to hunt around for some information… I can’t help you… I don’t use that stuff for anything…

Good luck…

:smile_cat:

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Thanks J

I believe I even coated it with Sanding Sealer prior to painting.

Difference of opinion here. I use similar MDF Frequently for layered door hangers. I use 1/4" plywood for the backer, but 1/8" MDF for the other layers. I always paint them, but I use acrylic craft type paint, not spray paint. It paints very nicely for me. I have never had much success with any spray paint trying to achieve a nice finish.

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I got some 1/8" mdf, smoked me out and didn’t like the results… always smells burnt…

Do you cut this on your laser?

:smile_cat:

Yeah, my CO2. Cuts great and fumes extracted out the shop window just fine. I love the look I get when it’s cut. Just the paint drives me nutz.

I guess I should revisit using it…

:smile_cat:

I have NO CLUE as to what’s in these products one -vs- the other. Never even really thought about layered work for giggles/profit…

It’s always been tumblers, bag tags, coasters… etc

I think I know of another suppler I could check out.

Thanks Tim.

I’m finding out that I don’t know much about painting.
Of course, I know 100% of everything else in this Universe. :slight_smile:

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This is an example of a 4 layer door hanger. Like I said in my previous post, the backer is 1/4” plywood and everything else is MDF.

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I am a cabinetmaker tradie,retired and now make toys, puzzles etc. I have used MDF for over 50 years and to be honest, it paints beautifully using acrylic (water based) paints. Like all timber it does require a light sanding prior on the face and a little bit more on the edges to ensure they are smooth. Two or more coats are usually required, with a light sanding between to get an optimal finish.
The piece can also be sprayed with a clear lacquer top coat for extra protection or gloss.
I have found that it also cuts nicely on my laser and engraves extremely well.
Enjoy and Have Fun

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Hi.

I doubt it’s much of a consolation, but no-one does.

With liquid chemicals, the required material safety sheet may provide some clues, but with solid products the legislation is somewhat looser so the manufacturers only list the bare essentials.
And when the batch changes, there’s no telling whether the materials and chemicals used are still the same as before or not.
And whether those said materials/chemicals are compatible with eachother, or not.
About the only way to find out is to do a trial run.

I have no experience with the paints You mentioned so I can’t offer any direct suggestions on what to use to acchieve good results.
Some sort of sealer is often used with porous materials when spraypainting, but that would obviously have to be compatible with both the material and the surface paint.
Unfortunately the suggestion You got wasn’t.
Assuming of course You used the suggested primer/filler.

One (automotive) painters trick is to use very thin veil-like coats of either the paint and/or compatible topcoat as a sealer, but that’s a bit tricky to do with rattle cans.

Just as choosing the compatible products, the application method of the paint is also a crucial part of acchieving the desired finish.
Especially in the desired timeframe and budget.

Rattle cans are often a viable alternative to a spray gun, but do have their undeniable disadvantages as well.
IMO the biggest disadvantages are the price (of the premium products), and the total lack of control over the airflow/pressure and the amount of paint.
Also, if the can is not equipped with a fan-nozzle, it’s rather hard to acchieve a good surface finish.

Hopefully someone has had the same problems with those same materials, found the solution, and will reveal it to the rest of us.

Regards,
Sam

:finland:

Good day peeps… Hope all is well.

I cut another piece yesterday and decided to just “LIGHTLY” spray the first coat with this MTN 94 paint. I took it immediately into the house to dry over night. It’s dry to the touch this morning. I’m going to add another “LIGHT” coat again, and take it to the house. Time will tell.

John I just tried it with my Acrylic paint that I had on hand. Applied very smooth, and dried within a minute or two. I should have left the cut piece in the main MDF board I cut it from to help keep the paint on the top and not run down the sides on some areas. I can fix that :slight_smile:

Sam I do have a gravity fed spray gun in a box never used, but I’m not doing production work, so I figure it will stay there… LOL

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I would also like to share a bit of my experience with MDF. There are probably as many manufacturers of MDF as there are factories that make plywood, with many different MDFs as a result. (HDF belongs to the same category, even if the composition and manufacture are slightly different).
What is critical when using these materials is formaldehyde, which is released by the sheets over time. Since 1980, the proportion of formaldehyde in the glue has been greatly reduced and today stands at 8 to 11% in the EU.
There is an extreme difference whether you laser cut MDF with 8% formaldehyde glue or with 20%. Evaporation of the glue can almost be compared to the evaporation of acrylic during laser cutting. BUT, you (I) don’t have that problem with 8-11% UF and MUF glue. A good indication of whether there is EU-approved MDF and/or your laser is correctly set for MDF/HDF is whether your material is wet at the cut edge or not.

As for painting MDF, I remove the wax layer that all boards have from the factory, with technical alcohol. It works fine here.
I use MDF/HDF a lot and fortunately I have a powerful industrial extraction system. My laser, laser bed/honeycomb and my extraction system are not smeared with tar when I work with these materials, no more than birch plywood emits.

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I have to get my kicks in here also. MDF is ground up wood and bark to extreme qualifications. I am not positive but the MDF core ply may be MDF with glue that has no formaldehyde or very small amount. That said: We manufactured children’s wooden puzzles containing MDF for over 45 years and sold them to almost every catalog company in the world. We had the product tested by a government approved laboratory continuously with the result being no formaldehyde content above permitted levels. We painted MDF panels by the thousand. Seal coat sprayed with lacquer white then proceeded to apply two finish coats of color lacquer. Have used latex paint sealer also.
I have used MDF core material as well as solid MDF with my CO2 laser with absolutely no smoke that you can discern. I do have an exhaust system.
BTW: Commercial MDF is not made of junk product, it is solid wood ground fine including ground bark to assist as a binder. The sheets are pressed under hundreds of pounds of pressure and heat to acquire different values of hardness.

Proper procedures mean a lot when you use any natural material.

Okay, I am finished with my rant.

3 Likes

Hi.

True, spray guns are better suited to production work and/or painting large surfaces.
The cleaning of the gun after painting is a major PITA even with better engineered quality ones, not to mention the fact that it gets rather expensive rather fast if used for minor tasks.

The spray gun is extremely flexible though, so it’s good to have one (or several :wink: ) stashed away, should the need arise.

Regards,
Sam

:finland:

Hi.

That’s not entirely true.

The varieties intended and sold for construction work are often made out of shavings and dust that is (or rather was) a huge problem for the mechanized forestry industry.
Just like particle board, OSB, (gypsum board in chemistry industry) etc. was created out of a waste problem back in the day.
And the eco-insulation materials more recently.

One could say -and wouldn’t IMO be wrong- that the companies just wanted to outsource their their waste handling, and even to be paid to do so.

The MDF varities intended for furniture manufacturing may or may not be the same, depending on the applied finish.
Which in turn mostly dictates what kind of VOC grading and other approvals the final product gets.

The toy industry You mentioned is a whole 'nother ballgame.
Every material used has to be approved individually, and the end product as well.
Most likely than not, a good portion of it will go through a childs intestinal tract anyway, so it has to be absolutely safe to eat and handle.
On those kind of applications it may be feasible to use fibers that are ground from “virgin” , selected material, using special machines with special lubricants.

But.

As a Beng.Mech. and as a someone from a country that not so long ago used to be one of the leaders in quality forestry products, I for one struggle to imagine why would go the lengths to intentionally pump the production costs up by using anything but the abundant waste -or byproducts if that sounds nicer- to make MDF.

The “waste”, “junk”, etc. we are talking about is squeaky clean if not intended to be pelletized or burned as is.
And often even if it is.
The amount of contaminants as lubricating oils and such is miniscule, and can be food approved if required.

The real problem with MDF, HDF, particle board, OSB, etc. isn’t IMO the fibers themselves, but the binding agent.
And that’s the reason I for one refuse to use those materials in living spaces, or in anything that gets in contact with living things.

It’s possible -but not feasible- to rely entirely to the lignine as a binding agent, so either natural or synthetic binding agents have to be used in order to get the material properties we require, in the price frame we are willing to pay.

Regards,
Sam

:finland:

Well my painting scheme didn’t quite go as planned. I thought I would pull out the sheet, and place the cut pieces back into it on a table, then just paint across the sheet area where the pieces were located. Some of the paint scraped off the brush, and leaked down the side of the pieces.

That’s not going to work. I guess I’ll just to paint each piece separately and be careful about it which isn’t in my skill set… LOL