MDO prepping problems

Mark Felder · Post by **Mark Felder** » Tue Sep 05, 2006 5:01 pm

Help! After 25 years of signpainting I still get problems with the edges of some MDO signs peeling after a short time. I've been using Ray Chapman's technique of first putting a layer of putty (Elmer's Exterior Carpenters Wood Filler) on the edges. Then sand leaving about 1/16" of filler on the edge, then 2 coats oil based primer, and 2-4 coats acrylic or alkyd finish.

Some edges are still good after 10-15 years, others fail in 1-2 years.

Any advice would be most appreciated.

Thanks,

Mark Felder
The Sign Shop
Gardiner, Maine
mfelder@gwi.net

Doug Bernhardt · Post by **Doug Bernhardt** » Tue Sep 05, 2006 9:30 pm

What has worked for me here in Canada is this...fill edges with bondo and sand (have also used epoxy at this stage)...sand board and 2 coats of oil primer followed by enamels and and an acrylic top coat like "Clearstar" the uv topcoat is terrific if you have west facing dark boards. Good Luck!

Mark Felder · Post by **Mark Felder** » Wed Sep 06, 2006 10:56 am

Doug

Do you just fill any voids with Bondo, or do you coat the entire edge?

Mark

Doug Bernhardt · Post by **Doug Bernhardt** » Wed Sep 06, 2006 6:25 pm

Mark...a little of both actually but particularly the voids. I hate seeing water get in and if the planks needs a real nice edge...the whole kit-and-kaboodle! I need to add also that quite a number of years ago a rep from our supplier gave a talk on recommended prep and his advice was an epoxy sealed edge...heck maybe both would be the best but you have my ways right there.

fayette pivoda · Post by **fayette pivoda** » Fri Sep 29, 2006 12:51 pm

I suggest breaking that hard corner at the edges of MDO, the paint film is thin as it wraps around the corner and failures seem to start there. After filling in the edges, I like to use a file to break the corner just enough to "take the edge off", then I'll follow up with a piece of sandpaper under my thumb. This lets the primers and paints keep a consistant film thickness as they wrap around onto the edge.

Hope this helps.

Mark Felder · Post by **Mark Felder** » Fri Sep 29, 2006 1:39 pm

fayette pivoda wrote:I suggest breaking that hard corner at the edges of MDO, the paint film is thin as it wraps around the corner and failures seem to start there. After filling in the edges, I like to use a file to break the corner just enough to "take the edge off", then I'll follow up with a piece of sandpaper under my thumb. This lets the primers and paints keep a consistant film thickness as they wrap around onto the edge.

Hope this helps.

Fayette, do you use any other sealer other than the primer and finish paint? Are they oil or water based? Lastly, how long do your edges last?

Mark

fayette pivoda · Post by **fayette pivoda** » Sat Sep 30, 2006 8:59 pm

I'm sure I've had a few failures out there but most seem to be doing good. I know of a couple at least 6-7 years old still looking good, edge wise at least.

I've just used Benjamin Moore's Fresh Start primer and then top coat with Dana Background or Chromatic Bulletin, 2 coats on nicer signs. In addition, on these nicer signs at least I'll use 3/4" material, fill in the gaps (Elmers Ext. filler), power sand the edges and do the round-over (both front and rear) as I go. As I said I usually use a file, on the downward cutting stroke I'll travel a few feet of distance (about 4-5 strokes per 96" side), & following up with 120 sandpaper under my thumb seems to do the trick.

The MDO I get is pre-primed so all I have to prime are the edges where the filler is, usually 2 coats and I'll wipe it off the faces as I go. Before I topcoat I'll wipe the entire sign down with a scotch pad, blow the dust off and then damp wipe it with laquer thinner or alcohol. When topcoating I'll do the edges too and wipe the drips off the bottom side as I go, when dry, flip it and do the same, repeat for the second coat. Even on 1/2" MDO field signs with a single topcoat I'll break that edge. And I cannot stress enough the importance of good prep.

Hope this helps.

Chris Lovelady · Post by **Chris Lovelady** » Tue Nov 28, 2006 3:15 pm

Fayette good to run into you again,

here in North Florida and South Georgia the temp range from morning to afternoon can be as much as 50 degrees. I have move away from bulletin enamals and have been using 100% acrylic paints. the edges and face are sanded and as Fay said the paint will not stick to the corner edges. so a slight round over with the sanding block. blow all the dust out of the cracks and then i use Elastromeric caulking to fill all voids. this has the greatest range of expantion and contraction. smooth it on all the edges of the mdo before any priming( i get all MDO raw) then we spray primer and then 2 finish coats. we use an airless sprayer and a gravity fed pot sprayer, for smaller jobs. never a failer!

wood putty seems to get hard and brittle over time and will crack! this has been my expereance. when Hand Lettering I have used bulletin enamels over laytex primer before but oil paints get hard and brittle over time as well and oxidize.

Lovelady