plywood or MDF for substrate

H

hschappell

Member
What type of substrate is best for veneering a top for an oval table approx.42 inches long by 25 inches wide? Does Mdf come in different grades? How many plys and what kind of plywood is best,birch oak etc? Where is best to buy these products?
 
Depends.  If historical authenticity is important, the answer is neither. 

If outgassing of formaldehyde to your home or your client's is important, then American made plywood, preferebly "apple ply".  Some of the american manufacturers are starting to introduce plywood made without formaldehyde glues - so called "green" plywood.  Don't buy chinese plywood from the big box stores - consumer testing labs have reported extremely high VOC with this material

If ultimate stability and no issues with chemical off-gassing and weight are concerned, MDF.  There are indeed different grades of fiberboard, but to my knowledge not necessarily different grades of medium density fiberboard.  For example, you can get HDF (High Density Fiberboard) were structural considerations are important. 

Of course, your choice may be influenced by the weight of your proposed substrates - MDF and HDF are quite a bit more dense than plywood, and require greater supporting sructure.
 
There are indeed different weights of mdf sheet materials. Two products come to mind -TRUPAN LIGHT, weighs approximately 80% of a standard mdf or about 80 lbs per sheet of 3/4" X 4' x 8'. TRUPAN ULTRA LIGHT, weighs approximately 60% of a standard mdf or about 60 lbs per sheet of 3/4" X 4' X 8'.

"There are indeed different grades of fiberboard, but to my knowledge not different grades of MDF."

MDF is "Medium Density Fiberboard"


Tony Joyce
 
Depending on the type of plywood you use you can get the grain telegraphing through the veneer. Birch plys like apple ply or baltic birch should not be a problem. You can also get plywood with 1/8"veneers of MDF on the outer faces and also phenolic paper though I forget the names. MDF is an excellent substrate for veneer. When I do a commecial job I use MDF core because it is a constant thickness and doesn't have voids. Because it is denser it resists dents better. On a table as small as yours weight will not be an issue. Be sure to veneer both sides to keep it stable.
Mike
 
I'm certainly no expert, but I have had real good luck using regular MDF from Lowes or Home Depot.  Nice and flat and takes glue very well.  Be aware - I did find a piece of metal in a piece once.  I hate to admit this, but we bought a table from Ethan Allen. It has a huge round top that is veneered.  This top weighs a ton!  It must be MDF that is more than an inch thick.  It's actually a very nice looking table, but gosh is it heavy.  I'm guessing the diameter is 5'. 

I recently built a chest that I used some striped mahogany veneer on.  I was concerned that the chest would be way too heavy if I used MDF.  So, I used 3/4 Baltic birch.  That worked real well too.  I made sure that the surface was good and smooth before I veneered it. 




Tony
 
"MDF is "Medium Density Fiberboard"

Yeah, I didn't write my post particularly clearly.  What I meant was that there's different weights of fiberboard - MDF and HDF, for example, but I'm not aware that there are different grades (quality levels, size of particulates, glues, etc...) within a particular class.

 
All, If I was advising, I would always recommend a plywood or block board for the veneering base, for these reasons, Strength, Weight, and Size, old furniture is made from real wood?
I now MDF comes from tree fibre, but in my book that is hardboard, (leaves of paper glued together)
But hardboard is: Not Real Wood.
                                     
                                Joseph Hemingway
                                      Sharing the tricks of the trade.
                                        40 years in business 1968-2008
 
Personally I have used both.  The only concern is that if any liquid some how slips through the finish or any cracks it will swell the MDF.  If any spillage did occur then there is very minimal concern.    Some may say that cracks are unlikely to allow liquids to collect, but the veneers these days are so thin and crack so much more then the past. I spoke to Silas Kopf recently and this same issue was discussed and he stated that finland birch, marine plywood, apple ply or baltic birch is the best.  Now, finland birch is very expensive in comparison to baltic or marine plywood and they all weigh differently.  So concerns one needs to be aware is to make sure is  flatness and weight.
Good Luck.

Freddy Roman
 
All
If historical authenticity is important, solid wood, yellow/or baltic pine was the material used by our (UK) past masters, early 1900's deal was the wood, or later Russian pine replaced the Canadian deal, for simplicity (no matching of narrow boards, fewer joints) sheet materials replaced solid timber, I remember particle board (Chip Board) arriving in the late 50s, the reps told us you can just? Run a mould on this new product, I remember thinking its like pushing against the grain, but all the time. (Brummer stopper took a bashing)
one of the best early sheet materials after Chip Board, was the forerunner of present day blackboard, its name was: Lammin board, it was 3/8 strips of timber for the core, instead of the 5/8 “ square pine/hardwood blocks now used on 3/4 thick boards, now that was very stable, but progress makes the better product un economic
So if historic authenticity is important, only solid timber can be used. But we all like?
An easier task. Am I correct?

                                                Joseph Hemingway
                                                    40 years in business, 1968-2008
 
Freddy,
I wondered about this so I did a test. I cut a piece of raw 1/2" MDF into 3 parts. I placed one part face down in a puddle of water for 5 minutes, I put another piece in a jar of water for 10 minutes. I blotted the two pieces and let them dry in the air. There was no measurable swelling of either piece in comparison to the third control piece.
Mike

FREDDY ROMAN said:
Personally I have used both.  The only concern is that if any liquid some how slips through the finish or any cracks it will swell the MDF. 

Freddy Roman
Click to expand...
 
Wow I am shocked I have a few pieces of MDF that have swelled do to a little liquid sipping through cracks of veneer.  At first I thought that the veneer may have been lifting but than I decided to strip the veneer and notice the a huge bubble.  Like I once stated Silas Kopf has some bad experiences of moisture bubbling up the MDF and ruining the piece.  So maybe you were lucky with this experiment.  I still use MDF on jobs here and there.  The only difference is that I am just a little more careful. 

Freddy Roman
 
Hi, An interesting post this, as I mentioned earlier, Hardboard was the four runner to MDF, when Hardboard is apply over a studded timber wall as a cheap covering, (finished surface). This was carried out in offices, etc. (1960)
The manufacturers instructions:  soak the back of the hardboard with water, before fixing, leave 30 mins, and then fix.
As it dried it became as tight as a drum skin.
This proves to me it is unstable, soak solid timber for 30 mins, then leave to dry, it dries the same size.
                                                                Joseph Hemingway
                                                                    1968-2008
 
MDF, Plywood, Lumber all of these are options for substrates.  Yet I think a wood core is the best option for substrates.  Mr. Phil Lowe taught me that if I had a wide board of say Mahogany or Basswood or Pine and cut this board into strips say 1x1 and by keeping track of strips and then flip every other one end.  Glue this material up and form the substrate and mill, shape, cut like you normally wood. What this technques does is help the material stay flatter and if you use rift sawn lumber or quarter sawn lumber then there will be very little movement or stress.  While flipping every other board end for end it retains the same grain direction on the outside faces.  The other option is that if you cut 1x1's and flip every other one end for end and then if you rotate the material from face grain to edge grain you are then making a quartersawn top.  I have used both of these options and it may seem a lot of work but it works and it is fun.  Oh ya one more thing.  After the top is made and if you cross veneer it with 1/16 thick material like Mahogany and then veneer the show veneer perpendicular to the cross veneer.  What you are doing is basically making plywood from solid lumber.  It is very good method & comes handy in veneering.  If anyone needs more info please feel free to email me @ [email protected]
 
Keep in mind that I am not encouraging or discouraging the use of MDF. I would tend to use period methods on a reproduction. My responses are to the original post. As to the swelling on your piece Freddy it sounds more like something particle board would do. I wouldn't recommend particle board to anyone.
Mike
-6 degrees F today
 
I think I still have the MDF with the bubble and some of veneer still on it.  I should take a picture to show you.

Freddy
 
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