Urgent-ish Again:Sanding/Keying Tempered Masonite

[Capt. Grimek]

I'm about to start sanding my tempered (smooth both sides) masonite.
I know that I should use fine sandpaper or sanding sponges.
Is 180 grit or 200 something appropriate for keying for a good primer paint?
A friend showed me that I only need to take the shine off the surface and that scratches barely
being able to be seen is fine. Is this correct?

Should I use a coarser grit and see very evident scratching? Anyone have pics of what this should look like? I've looked at artist sites as they often paint masonite but no pics of the roughing/keying steps so far.

I'm "hip" to wood surfaces but masonite-no one at lumber yards, paint shops, on the street, seem to
know or agree on what's correct regarding everything from coving to sanding to painting to whether BOTH shiny sides are truly tempered or only one. NO wonder there are so many threads about masonite
here!

Many thanks for all of the help on several thread with "masonite world".
This is kind of urgent (now that I've got the coving info.) as I hope to start sanding/priming tomorrow
and don't want to waste good quality an expensive primer. I plan on priming both sides, but just the smooth back side for now until it's up.

I was also concerned about priming where the backing tape might touch the top and bottom back edges after priming. Should I leave a small unpainted spot on those small edge areas until we tape and mud with vinyl spackling? Anyway pics of proper level of keying are the main thing for now.

Many many THANKS everyone! I'm FINALLY getting the train room started!!!

[doctorwayne]

Once again, I don't see any reason to sand the Masonite, tempered or not.  Any good-quality latex paint will stick to it just fine if the surface is clean and free of grease or oil.  As for painting the back, whether it's smooth or rough, I wouldn't bother with that either, unless your layout is in the shower. (And in that case, your drywall screws will rust anyway.)   Finally, for painting the face of it, wait until you've got it in place and the joints are all finished.  You're liable to put fingerprints on it during installation and, if you're taping and mudding the seams, it'll get scuffed when you do the finishing work.

Wayne

[CSXDixieLine]

My Masonite is installed smooth/shiny side out (to the front). I have primed one 8 foot section and the my primer adhered to it great without any preparation. I used Zinsser 1-2-3 Bullseye primer which was purchased at The Home Depot. Although I have not used this primer for backdrops before, I did use it for all of the trimwork in the basement where the layout is located. Six years and no problems to date 

Do I read your post correctly in that you are installing your backdrop rough side out? Seems like you would want a smooth surface to paint the background scenery on.

Jamie

[Capt. Grimek]

Thanks Wayne. I've read on several masonite painting sites to paint both sides to avoid moisture absorbtion from the air. My shower IS right next door and if my wife forgets to shut the door to the train room, turn on the bathroom fan or we get some moist air from the kitchen steam cooking, etc. I thought it couldnt hurt.

In an earlier post/thread, I did say that I was going to use the crosshatched/back side out but as I've read up, interviewed painters, etc. I'm using the smooth side out with a laytex primer (BenJamin Moore) and a laytex paint overcoat after.

Many sights say to sand the smooth side lst. Some don't. (See why all the posters here are so dang confused?)

I'm concerned about the waxes and oils used in the manufacture of the hardboard and considered an oil based primer but the train room has no windows and oil based will stink up the house a lot more than laytex.

[doctorwayne]

Here's a link to a lot of information about Masonite and other hardboard.  I learned a few things and you might, too.   Different types of board accept paint differently and S1S (smooth one side) is more flexible than S2S.  Also, the two sides of S2S are not identical.  Lots of reading, but worth checking out.

Wayne

[Capt. Grimek]

Thank you. That was most informative and very helpful. I've been reading as much as I can (and asking questions as much as I can). There was quite a bit of info. in your link that I haven't seen elsewhere.
I think I've got my game plan now.


Of course Lowes or Home Depot isn't "telling" what manufacturing method was used. Wet, dry, etc.
which would be most helpful...

[lvanhen]

You've already got the Masonite link, and that pretty much covers painting.  DO NOT SAND THE SPACKLE!!!!!   For that matter, don't sand anything indoors if you can help it!!!  Spackle can be "sanded" with a damp sponge.  Even years after application, spackle will soften with water as long as it hasn't been painted.  Smoothing with a sponge creates no dust, which is one of the biggest bug-a-boos for a model RR!!  Dirty track is one problem, but what spackle dust will do to the innards of a loco YOU DON'T WANT TO KNOW!!  My

[doctorwayne]

You've already got the Masonite link, and that pretty much covers painting.  DO NOT SAND THE SPACKLE!!!!!   For that matter, don't sand anything indoors if you can help it!!!  Spackle can be "sanded" with a damp sponge.  Even years after application, spackle will soften with water as long as it hasn't been painted.  Smoothing with a sponge creates no dust, which is one of the biggest bug-a-boos for a model RR!!  Dirty track is one problem, but what spackle dust will do to the innards of a loco YOU DON'T WANT TO KNOW!!  My

Another good reason why layout room preparation should be done before the layout is even started.  This includes walls/backdrop, ceiling, and floor (if necessary).  Don't forget lighting and other electrical work, too.  This may seem boring compared to "getting some trains running", but you'll end up with not only a better layout, but a more pleasant environment in which to build and operate it.

Wayne

[jrbernier]

Capt,

  I think you reading into this project too far.  I have 1/8" Masonite backdrops that have been installed since 1988.  They were screwed to 2x2 firing and then painted with a standard interior latex paint.  As far as moisture; one side of the layout is against the laundry room.  I am sure the folks who built your house did not paint/seal the framing before hanging the drywall!  I have had no problems with moisture(and I live in Minnesota with wild temp/humidity swings).

  I used sheetrock screws to attach the Masonite, and used the normal drywall mud/tape/sanding to cover the cracks.  Only one small hairline crack ever materialized on a 25' section of the backdrop(and you really have to look for it).  I have a 25' wall and a 20' wall that are exteior walls that the backdrop is attached to.

For the corners, I built 24" radius plywood formers out of 1/2" plywood and screwed them to the wall.  the Masonite just wraps around the curve.  I am sure you can get a small radius with 'soaking', but you can get down to 24" radius with no problems.  If your backdrop is 4' deep, I would use 3 formers.  Mine is 24" and just has one at th top and at the bottom of the Masonite.

Jim Bernier

[Capt. Grimek]

Thanks guys.
I just wanted to be sure I'd only have to do this ONCE as the alternative was too nasty to imagine once things were scenic-ed, etc.
My layout room is above a damp (all year) crawl space and over a damp cellar that has an 1/8" to 1//4" of water on the cement floor even with sump pumps from Oct./Nov. through June or so.
Just erring on the side of caution wherever possible, especially with the varied
advice/methods I've seen over the last couple of months on this and other forums.
The link Dr. Wayne posted helped a lot to settle some issues.

I won't be using framing or firring strips so I wondered about the need for the corner bracing.
JR, do you think construction foam sheet would suffice in place of plywood?
It would be an on hand solution that is a "compromise" between your corner ply pieces and
Dr. Wayne's report that he didn't use or need the corner bracing at all?

I am definitely getting the room ready before any bench work begins. It's just that I'd like to get the back drop done in this next week or so as I have access to a free (my favorite price!) drywall tape/mud guy.
He'll be sponging the vinyl spackle, thanks I. for the warning regarding sanding.
I wanted to sand to avoid oil/wax issues with the manufacturing process seeing as I have no way of really knowing what "style" of masonite I have. By the way I., I'm an old "Jersey boy" myself. Passaic County.

[BurbankAV]

That's a great link, Wayne!  I'd put that in the "required reading" column for anybody working with the stuff!

Thanks!

Peter

[jrbernier]

Capt,

  I am sure some 1" or 2" foam will work, but I suspect plywood will be just as inexpensive.

Jim

[Capt. Grimek]

Thanks Jim. I already have some foam as opposed to traveling and buying more plywood right now.

I was sanding/keying all afternoon out in the driveway until it started sprinkling. I'm gonna try and do another panel or two tonight (indoors) once my wife goes to sleep. Just taking the shine off of the tempered surface with a fine sanding sponge.
Paranoia
wins out here, after all, I'm afraid. :-0

[jrbernier]

  I just do not understand why you are 'sanding' the shine off of the Masonite.  My thoughts are that you will raise 'fuzzies' and when you paint it, they may show.  I just wiped my Masonite with a damp cloth after the mud/tape/sanding phase and painted it with an interior flat latex, using a medium knapp paint roller.

  BTW, what is 'keying'?

[Capt. Grimek]

"Keying" is a term commonly used for micro scratching/cross hatching of the gloss surface layer
in order to give the base coat of paint some "bite" to adhere better to the surface, reducing the chance of flaking or peeling or orange peeling later. It's used in boat finishing work all the time and I believe in many other applications such as general house painting, auto body work, steel work, etc. My masonite gloss surface is still intact overall, just scratched up to a slightly more matt-ish finish. I did go a bit heavier where the vinyl spackling/mudding and taping will take place. Those areas might fuzz....but they'll be covered with the tape before priming. I won't be priming the front side (shiny side) until the back drop is screwed to my walls. I'll be doing the backs first.

This was advised by my drywall finisher and on several sites in the past as well as some paint dealers I spoke with. I sure hope it doesn't cause fuzzing! (See, now I'm paranoid all over again!) I would think that a coat or two of good quality primer would fill any fuzziness, but I'll be finding out by the beginning of the week.

I've been reading here that some folks painted right over the masonite's shiny surface without issue
but I'm kind of amazed that paint is sticking long term over any tung oils or waxes or anything else
that was used in the manufacturing process. (Sometimes even if the material itself isn't coated, the rollers or presses are.) Well, it's too late now, for me! We'll see what happens as I begin painting. With any luck,
I'll be starting today. Here's hoping.

Ok, back after priming the lst panel. No fuzzing. Looks purty. Keying is done with only 200 grit or finer, I forgot to say that above. My M.R. buddies in WA. State have all primed the backs if their panels. It's so damp and soggy here for 8-10 months out of the year most years. (N. of Seattle) they all felt they could sleep better at night or if they had to leave the house for a trip and have the train room shut/locked with
no heat. I have no heat in my room unless the door is open to the rest of the house.

I did leave the area I'll be taping and mudding (probably with vinyl spackling) unprimed until my taper calls back to be sure taping and spackling will stick to it ok. Have you guys taped and compounded/mudded over your primers or paints?