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Discussion Starter · #1 ·
The house we are building has alder wood tops on many of their desks and custom built cabinetry.
We are working on finishing the alder wood tops and have applied 4 coats of polyurethane mix, but are finding that it is still scratching easily when say we write on a piece of paper on it due to the softness of the alder.
We need these tops to be durable for writing on and general day to day use as desks (it was the homeowner who decided to use alder...couldn't persuade her to use another wood).
Looking for a hardener additive to harden this finish up, or an alternative finish that will be hard enough to resist scratching. Checked into Waterlox and a few other finishes...having trouble finding specific hardeners.
Thanks
 

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Just for the sake of clarity, what kind of poly are you using right now? It sounds like you're already using a two part poly, which is about the hardest stuff out there. If you're actually just using a one part oil or water based poly, you should try switching to the two part stuff. If the wood is still marking under the two part poly with a good 5 mil build, I think the wood is just completely inappropriate for the purpose and there's not much you can do to make it work. This is always the problem when clients start hijacking decisions about materials that they really don't understand. Good luck mate!
 

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Discussion Starter · #3 ·
I'll find out what exactly he is using, but someone had mentioned to him that gym floors use hardener additives to make them tough...he seemed to be interested in finding out more. Any thoughts?
 

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May not be able to help you here, as I don't know of any additive that could actually harden wood in terms of raising it's number on the Janka scale (thus making empirically harder). For years Watco Danish Oil claimed (falsely) that their oil finish made wood "25% harder" but this was completely debunked several years ago. Watco stopped making that claim since then. Maybe there's a product out there that I'm simply unaware of, certainly a possibility, but I have trouble imagining what it is. Most gym floors are hard maple coated with a number of high-end finishes. Some use two part poly, some use high-tech vinyl finishes (not really an option for smaller outfits as it's difficult to work with and requires special equipment), some are using UV cured finishes now I understand. I don't do gym floors so I can't tell you all that's out there at the moment.

The big key here, is gym floors start with wood that's a heck of a lot harder than what you're working with. Most gym floors are traditionally hard maple (Janka 1450). Newer floors can be made of bamboo (Janka 1762 for solid bamboo). You're being forced to work with alder (Janka 590) which frankly is very soft wood. Even coastal Douglas Fir available at a big box store. (Janka 710) is harder. Alder is just the wrong choice for a table top or desk top. Your best bet is to talk him out of this misguided choice, show him some better options and move on. If he's hellbent for leather on using the alder, I'd put a two part poly on it and tell him there's no warranty whatsoever. You've put the hardest finish you can get on it, but nothing can magically make a wood as soft as alder hard enough to deal with heavy use. Good luck to you, let us know how it works out.
 

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Who is the original poster here? The craftsman making the cabinets and desk? or the homeowner? Or a third party?

I ask this because it is good to know the experience, knowledge and background of the person to whom we are answering.

George
 

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Discussion Starter · #6 ·
I am the CAD designer/office manager at the site- the painter here is a professional, and asked me to look into this for him as he's never dealt with it before.
So is something like tung oil not going to help either? I've just been trying to research various products as we're almost ready to just start experimenting trial/error at this point. We also have hickory tops to finish and want to make sure we're on the right track. Thanks for the help
 

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All oil finishes (tung included) are the softest of all finishes and do nothing to harden wood whatsoever. In fact, they're the least protective of all finishes in just about all regards. It may not be a good idea to put tung oil down on the wood at all in this case as it could potentially cause problems with adhesion of a harder top coat. Sounds to me like someone got wind of the "25% harder" hooey that Watco used to push at some point in the past, and is now stuck on it.
 

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Dan K has the simpliest solution and pratical. Minwax makes a woodhardener for damaged/soft wood but is directed towards rot. I've used the product for "hardening" back the fibers for repairs but not as interior. This product smells like a thinned fiberglass resin and soaks into wood quickly but let dry between coats.

I AM NOT saying this is what to do (it's a clear liquid) but if I/they are determined a natural look ( NO GLASS) then I'd test this on other sample. Also at one time "Formica" ?? offered wood laminate veneers that had the hard countertop finish inbedded.

Have a Blessed day,
Tim
 

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Are we mixing 2 concepts here?

QUOTE :....
The house we are building has alder wood tops on many of their desks and custom built cabinetry.
We are working on finishing the alder wood tops and have applied 4 coats of polyurethane mix, but are finding that it is still scratching easily when say we write on a piece of paper on it due to the softness of the alder.

First, is the wood itself Alder, Pine, Poplar.... what ever, but all on the "soft" side as was nicely referenced above.
Second, we have the finish which is on top of the wood. If the finish is too soft then any pressure from a writing pen or pencil will leave "pressure" marks. The answer to this issue in my opinion, is a harder finish.

So now we have way too many choices...spray on, roll on, pour on, brush on... Then we have pre-cat, 2 part, air dry, water base, solvent based etc. Based on the environment where the items are, can you spray at this point?

My opinion is to make a decision "tree" to help decide.
List the categories above like: SPRAY... ROLL.... BRUSH.... POUR ON
Then below list the types of finishes available in each category.
Then list the hardness factor below those. You may end up with 3 choices from which to decide.....then COST and TIME will determine the "best" method. ;) bill
 

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OOHHH !!!! My head hurts now:eek::laughing:!!! TOO MANY decisions. I'll go back to the above and GLASS IT:thumbsup:. See no more thinking or finishing!!!

Just my opinion.

Have a Blessed day,
Tim

As the old KISS saying goes: Keep It Simple Stupid!!!!
 
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