Finishing MDF or Trupan to a smooth surface

[Brady Watson]

Ok Guys...I need some help from some of you finishers out there. I am working on a large 3D relief project using Trupan (and have tried MDF as well).

The problem I am having is that I cannot find a product to seal & raise the hairs that is easy to sand AND leave a smoooooth surface. I have tried watered-down Titebond I, Epoxy, wood hardener, Deft SS, Kilz, FSC88, Zinser B-I-N and a host of other products in hopes of knocking off the hairs and getting a consistent surface. Epoxy and FSC88 worked pretty well, but after sanding, there are dips/voids/pocks in the surface...I need to spray a smooth enamel finish on this and I am getting to the end of my rope!

Thanks!
-Brady

[bleeth]

Duratec from Dupont-First coat looks like heck-Sand it and apply the second coat and it sands like glass. (Used by FRP plug builders everywhere).

Dave

PS: The cutting is the easy part-Finishing is h----------

[Brady Watson]

Dave,
I have Duratec here...(made by HawkEye)...I use it for FRP stuff. Didn't think to use it here...

Would you sand the Trupan 1st?...or just spray, sand, spray? I wish it wasn't 'nasty-polyester' scented...

-Brady

[paco]

I would spray first prior to any sanding, so after that, I would hope that it would hold the hair while a soft sanding... maybe a second step to remove more if need. I'd look for something that would soak in some of the surface of the material.

[mikejohn]

The Duratec range of products(marketed by HawkEye in the States), could have another name in Europe, as I haven't found it by Googling. In fact I have found another product with this name. Anyone know what name these products are marketed in Europe, and by whom?

...........Mike

[joe]

Here's my favorite.

Bulls Eye shellac. It's a good base for allmost everything and sands smooth.

For a really slick surface over shellac, High build primer.

j

[bleeth]

If your relief is done with a small step asnd has mimimum ridges you can probably go straight to priming.

Dave

[patricktoomey]

I agree with Joe, Shellac is what I almost always use on MDF or Trupan. First I rub the whole thing with an abrasive 3M pad to get the worst of the dust and hair off and then I start with a thin cut of shellac, like 1 lb (1 pound of shellac flakes to 1 gallon of alchohol). That soaks in enough to raise the remaining hair which you can easily sand off. One more coat if you need it and then build to your smooth topcoat with a high build primer.

[stickman]

What are you using for a high build primer?

Could Shellac be sprayed with an HVLP?

Jay

[gcoding]

I had a job out of mdf that I was going to paint a dark color. Instead of sanding the hair like stuff from the mdf. I justed used a plumbing soldering tourch long enough to burn the fibers not the relief..

[handh]

We don't do signs but cabinets. We use a product by Sherwin Williams. It is Sherwood Wood Surfacer and Lacquer. It does a great job on mdf and fills the surface and sands wonderful, gives you a smooth surface to paint ontop. Yes we use a HVLP to apply you have to thin.

[Brady Watson]

I would love to use shellac too...but it seems that the 1st 3/16" of the trupan is pretty dense. Once you go below that, it has LARGE hairs to it. I tried shellac, but it didn't work out as well as I had hoped (this is the 1st thing I try for everything...I love the stuff). Tried the torch buring off the hairs...worked OK...not so well on 'peaked areas'. Tends to recede the RLF if it is thin.

So far the only thing that I have found that *almost* gets me there is FSC88-WB or Epoxy. I have tried pre-sanding and not sanding. Not much of a difference. The real problem spots are where sanding has yanked out hairs and now you have a void.

More testing today...will be trying 2 coats of epoxy with NO sanding. Hopefully this will resolve the 'yanking/void' issue. I REALLY do not want to have to bondo the entire surface....

Also tried glue pre-sanded, dried and sanded and dried and re-machined. Re-machining just rips the surface out in chunks when you do a .01 surfacing toolpath...

I've got more checmicals over here than you can shake a stick at right now!!!


Thanks for the feedback so far!
-B

[gerald_d]

That dense, air-tight, glue-filled, nasty-on-the-cutter-and-lungs MDF is what our moldmaking clients prefer when large areas of "inner core" have to be finished. That light grade Trupan sounds like it is a haystack that needs a gloss finish.

[Brady Watson]

Just returned from the shop. It looks like Kilz brushed on might be the winner. Still testing...more when I have something.

-B
PS - Yes...it IS like a haystack

[joe]

Brady,

Your right about the surface texture of Trupan. I've also found it to be of rather inconsistant.

My reason for using shellac is for quick sealing off of the surface. It has very little filling properties on this material. Next I use a stiff bursh to smooth the surface. A dish scrubbing one should do, if it is very stiff. Next, a couple coats of High Build primer.

You can speed things up, on the first coat, with a spray can of shellac. I can gererally finish a job in a very short time with this combination of sealer, primer.

I know you are very skilled with this area and know you will find a solution that works for you. If I can be of assistance, feel free to call.

J.

[dmidkiff]

Brady,
I have painted a few MDF cabinet doors. I sand the milled areas and prime with Kilz2. Usually one coat but some doors require 2 coats. I follow this with sanding and 2 coats of quality acrylic latex, sanding bewteen coats. Hope you find the right combo.

[Brady Watson]

I rolled on 2 coats of Kilz regular late yesterday. 1 normal, one heavy. At some point today I will sand it and see how well it works.

Dave,
Did you see a difference in finish/sandability between Kilz original and Kilz2?

Thanks!
-Brady

[dmidkiff]

Brady,
Have never used Kilz original where I needed to sand,and have not used it since finding Kilz2. Kilz2 sands great and the surface is smooth when final coats are done. I apply with Sraytech sprayer from Lowes. Never had any luck with keeping brush marks out. Sanding rolled surface may be hard as well.

[joe]

Yep, Dave is correct about the surface textures left behind with rollers and bruses. However Brady hasn't given us enough information with reguard to the type carving he is doing. Are there large flat surfaces to cover or very detailed, deliclate area's?

Either way, a gun will allways finish out smoother. When I look at the work done by master carvers such as Doug B., www.bernhardtsigns.com (http://www.bernhardtsigns.com) the slight imperfections are a plus.

Trupan is a dream for woodgrain textures and finishes however I don't think this is the direction he's going.

J.

[joe]

woops,
That's

www.bernhardtsign.ca (http://www.bernhardtsign.ca)

[edcoleman]

double woops, Joe. The link is:

http://www.bernhardtsigns.ca/

you forgot the last "s"

[joe]

Thank you Ed.

[Brady Watson]

Thanks guys...

Yes, Joe, I haven't given any detail of the carving yet
I promise I will take lots of pics when it is all done!

As serendipity would have it, the customer liked the texture that the roller put on and the finish coat on top. Yep...hairs poking out and all. It turns out that when you stand 10' away from it (where most will see them) the light reflected off of the 'roller scales/waves' gives the design and entirely new dimension. So it's really serendipity do-da actually...no more sanding!

Thanks for the input! Pics to follow when project is complete.

-B

[paul_z]

Dave,

How much time does it take to cleanup the spraytech pump/line/gun? Have you developed any shortcuts?

Paul Z

[dmidkiff]

Paul,
I use the 25' hose supplied with the sprayer and it only takes a few minutes to change colors. I always use water base paints and just pump water though until the color is diluted and change to the next color. If I am going to store it for a while I run water though until it it almost all water and then clean the gun leaving water in the line.

[paul_z]

Dave,

Thanks for the info. Being able to minimize cleanup time makes the spraytech look even better from a cost perspective.

Paul Z