Painting MDO Plywood?

[zool]

Re: Painting MDO Plywood?

That system says to prime 1st for wood/synthetic

SYSTEM RECOMMENDATIONS
WOOD / SYNTHETIC WOOD
1 coat: C312 UltraTech Int/Ext 100% Acrylic Wood Primer
2 coats: 628 Aro-Plate II Semi-Gloss

http://comex-paint.com/pdf/Frazee 628 Aro-Plate II Semi-Gloss_PDS 08-2012.pdf

 

[jigngrub]

Re: Painting MDO Plywood?

I'll be doing a splatter paint job (to match the existing paint), which will result in a rough-textured finish. So, I won't need a primer coat for an ultra smooth finish. Based on responses it appears I won't need primer for top coat adhesion as long as I sand the resin surface.

I haven't had any problems painting over epoxy resin without a primer, I consider the first coat of paint the primer. Just sand and make sure the surface is clean and dry and start painting. I suggest at least 3 coats of paint and then your spatter coat.

If I remember correctly we're just talking about a small step deck on the bow of a small aluminum boat.

 

[Woodonglass]

Re: Painting MDO Plywood?

I hope we are ALL clear on the differences between MDO and MDF!! MDO plywood is constructed exactly like any other Exterior Grade plywood with the exception of the final layer/lamination being made up of high pressure paper/resin which gives a very smooth surface to the material. This layer can be on one side or both. This pdf will give you info on the product. http://www.pacificwoodlaminates.com/img/PDFs/PlywoodGuide.pdf

As JNG stated it is used in the Boat Construction industry all the time. There are different grades of it but it's all good stuff. For transoms, stringers and decks it's a very good product especially if you're using epoxy. Poly takes some extra prep work.

MDF on the other hand, IMHO has not place on a BOAT...PERIOD!!!!!

JUST my 2?!

 

[minuteman62-64]

Re: Painting MDO Plywood?

That system says to prime 1st for wood/synthetic

SYSTEM RECOMMENDATIONS
WOOD / SYNTHETIC WOOD
1 coat: C312 UltraTech Int/Ext 100% Acrylic Wood Primer
2 coats: 628 Aro-Plate II Semi-Gloss

http://comex-paint.com/pdf/Frazee 628 Aro-Plate II Semi-Gloss_PDS 08-2012.pdf

That's what it says on the can also. However, the salesman at the Frazee paint store said no primer necessary on regular plywood unless I'm looking for that ultra smooth finish (I didn't ask about MDO because I wasn't contemplating it at the time). That's why I'm here - I'd put more stock in you guys saying ".... I did it this way and here's how it worked ... " than what a salesman in a paint store, with unknown credentials, says.

 

[Woodonglass]

Re: Painting MDO Plywood?

If you use MDO and that Paint then I'd use the Primer but as every body knows, I'm just an...

That THINKS he KNOWS EVERYTHING!!!!

 

[Lone Duck]

Re: Painting MDO Plywood?

i hope we are all clear on the differences between mdo and mdf!! Mdo plywood is constructed exactly like any other exterior grade plywood with the exception of the final layer/lamination being made up of high pressure paper/resin which gives a very smooth surface to the material. This layer can be on one side or both. This pdf will give you info on the product. http://www.pacificwoodlaminates.com/img/pdfs/plywoodguide.pdf

as jng stated it is used in the boat construction industry all the time. There are different grades of it but it's all good stuff. For transoms, stringers and decks it's a very good product especially if you're using epoxy. Poly takes some extra prep work.

Mdf on the other hand, imho has not place on a boat...period!!!!!

Just my 2?!

yup!!

 

[zool]

Re: Painting MDO Plywood?

That's what it says on the can also. However, the salesman at the Frazee paint store said no primer necessary on regular plywood unless I'm looking for that ultra smooth finish (I didn't ask about MDO because I wasn't contemplating it at the time). That's why I'm here - I'd put more stock in you guys saying ".... I did it this way and here's how it worked ... " than what a salesman in a paint store, with unknown credentials, says.

The reason for the base primer is not for appearance, its for adherance....used as a tie coat, not a sandable build coat. The deal is, base primers are formulated to mechanically bond to the substrate, then the paint is formulated to chemically bond to the primer....basically the primer has better adhesion properties. Ive cheated on this many times, most times it was fine, but other times it was not and the finish failed.....worst case scenario is it fails and you have to redo it....

 

[jigngrub]

Re: Painting MDO Plywood?

The reason for the base primer is not for appearance, its for adherance....used as a tie coat, not a sandable build coat. The deal is, base primers are formulated to mechanically bond to the substrate, then the paint is formulated to chemically bond to the primer....basically the primer has better adhesion properties. Ive cheated on this many times, most times it was fine, but other times it was not and the finish failed.....worst case scenario is it fails and you have to redo it....

If your weren't going to sand before painting I would definitely say prime, like if you were painting a very large area that would be too labor intensive to sand. Sanding before painting will create the mechanical bond needed.

Next is, is the cost of the primer worth buying for a half or less of a sheet of plywood? For just one coat of primer?

 

[fishrdan]

Re: Painting MDO Plywood?

Original seats were MDO plywood, appeared to be painted with an oil based paint w/o primer. Held up well for 30+ years. I re-painted one of these with good quality oil based paint (with out primer) and that (applied over a well aged MDO surface) is holding up well.

If the original paint was un-primed, and held up well, I would go back without primer. I would scuff sand the surface though.

I have seen a few cases were the top coat failed due to the primer not bonding to the substrate well (different things, not specifically MDO),,, so I don't always use primer if I feel it not going to hold up well. And since you have all ready seen that unprimed MDO holds pain well... Well?...

 

[zool]

Re: Painting MDO Plywood?

Next is, is the cost of the primer worth buying for a half or less of a sheet of plywood? For just one coat of primer?

I guess that depends on how much one values his/her time, and how lucky one feels....is it worth saving a few bucks on primer, then have to look at failed chipping paint a year or so down the road?....like i said, Im guilty of the same...if I was charging for the job, and didnt want to risk a comeback..I would definately prime....for a personal project, i cut when i feel lucky.

 

[jigngrub]

Re: Painting MDO Plywood?

I guess that depends on how much one values his/her time, and how lucky one feels....is it worth saving a few bucks on primer, then have to look at failed chipping paint a year or so down the road?....like i said, Im guilty of the same...if I was charging for the job, and didnt want to risk a comeback..I would definately prime....for a personal project, i cut when i feel lucky.

Speaking from experience, I have 3 coats of exterior latex paint on top of 3 coats of epoxy resin (leftover from my boat project) on all the exterior door frames of my house with no primer between the epoxy and paint. It's been that way for 2 yrs. and I don't have the first chip yet, and you know how exterior door frames take a beating on a daily basis.

If it was my project to do, I'd take that primer money and buy a quart of epoxy resin and put 3 or 4 coats on that piece of plywood and then 2 or 3 coats of paint and forget about it.

 

[zool]

Re: Painting MDO Plywood?

Speaking from experience, I have 3 coats of exterior latex paint on top of 3 coats of epoxy resin (leftover from my boat project) on all the exterior door frames of my house with no primer between the epoxy and paint. It's been that way for 2 yrs. and I don't have the first chip yet, and you know how exterior door frames take a beating on a daily basis.

If it was my project to do, I'd take that primer money and buy a quart of epoxy resin and put 3 or 4 coats on that piece of plywood and then 2 or 3 coats of paint and forget about it.

Like you said, its only small pieces...so you do what you feel..

The thing is, just for imformational purposes, some Alkyd based paints can have a chemical reaction to epoxy resin, not unlike the reaction you get from using a polyester based resin over epoxy based resin.

From System Three:

"To do a test patch, coat a small area with the painting system selected to make sure that each paint layer dries properly and adheres well to its substrate. One reason for doing this is that epoxy resins, despite sanding and long cure time remain chemically active to certain components of alkyd paint and varnish systems. Generally, epoxy primers and LPU paints are compatible with epoxy resin coatings and may even chemically bond. However, some of the alkyd enamels and other one part paints and varnishes may not properly dry on epoxy resin coatings. The free unreacted amine in the epoxy resin coating interferes with the action of the metallic driers in some of these paints. If this happens the paint may surface dry but remain soft and tacky next to the epoxy resin surface.
A similar chemical phenomenon occurs between the amines in epoxy hardeners and the peroxide catalyst used in polyester and vinyl ester resins and primers. The amines inhibit the action of the peroxide catalyst, preventing cure at the interface. For this reason, it is not possible to “gel coat” finish cured epoxy without specialty barrier coats and it is very risky to use peroxide cured polymers directly over cured epoxy resins. Besides, gel coats don’t look all that good when applied to a male form. Their best use is against a polished female mold. For the same reason you should not use polyester based putties over an epoxy."

I dont believe the op ever used the product he has, and most likely its not what the factory used, so its a gamble based on info out there, plus, the paint system tech sheet recommends priming it, but they sell the primer so they may as well rec it

Not looking to make an argument with you jig, just putting this info out there... but ill just defer to the 1st line in your signature