The Wood Filler & Epoxy Test (Year 1)

By Scott Sidler July 6, 2015

wood filler test year 1One of the most popular posts on my site for the last year or so has been The 7 Best Products to Patch Wood. With over 160 comments and well over 100,000 page views I took the hint that people want to know about wood filler and how to patch wood.

So, 1 year ago I made a test board of some of my most used wood fillers and epoxies to see how they faired in the Florida climate. I’ll be revisiting their progress every year so you can always check back to see how things are holding up (or not).

One notable product that is absent is Durham’s Water Putty which I rarely use anymore. I’ve already done enough testing (by accident) on how Durham’s holds up when exposed to the elements. If it is primed and painted it does a nice job, but without priming and painting it fails very quickly so I generally stay away from it for any exterior repair now. Live and learn.

I’ve included affiliate links to the products below if you would like to buy some of these fillers for yourself and have Amazon give me credit for it. Thanks for the support!

The Conditions

I’ve tried to be very diligent in making this test as scientific as possible. I’ve outlined the rules and conditions I did the test with so you can duplicate my results in real world situations.

I drilled out a 1/2″ deep hole with rough edges to try to simulate a chipped or gouged board and filled the hole above the surface and then sanded level. Here are the conditions:

  • The wood fillers and epoxies were all mixed and applied according to the manufacturer’s specifications.
  • The wood use was a piece of 1 1/2″ thick rough sawn cypress
  • The sample was laid horizontally outside for 1 year
  • The wood and fillers/epoxies received no pre-treatment, primer or paint other than WoodEpox which was used as per the manufacturer’s instructions with LiquidWood prior to application.

The wood was left in my backyard which is a very sunny and wet place so there is a significant bit of algae growth that developed on the board which I thought added a good level of field testing to the fillers to see how they stand up to the harshest conditions.

All the filler and epoxies were applied and left to cure/dry until they were ready to sand smooth. I ranked all the fillers on a scale of 1-10 (1 being the easiest and 10 being the most difficult) regarding their ease of application and how easily they sanded and then noted the amount of time required for drying/curing. Here’s what I found:

WoodEpox

  • WoodEpox
    WoodEpox after 1 year

    Ease of Application: 6

  • Ease of Sanding: 2
  • Ready to Sand: 1 hr 30 mins

Application: I use this product all the time. Compared to some of the regular fillers it is a bit more work to apply since it is a 2-part epoxy that requires proper portions and mixing of 2 different materials, but for a 2-part epoxy it is by far the easiest I have ever used. There is also the additional step of mixing and applying the LiquidWood consolidant first which is the main reason it received such a high number for the ease of application.

Drying: It took longer than all of the other fillers to be hard enough to sand (4 times longer than the quickest one!). Quick drying is not always best, but it is a feature to consider. In my shop we have begun using heat to help WoodEpox cure faster when necessary.

Sanding: The sanding was a cinch. It easily came right back down to level and gave a nice smooth surface.

Results: Over this first year I noticed a very slight bit of shrinkage to the patch, but it has been very, very minor. There is also a slight cracking on one side at the joint with the wood. We’ll see if this continues to worsen over time. I was surprised that the epoxy developed algae growth more than any other of the fillers. I don’t know if this will affect its performance over time, but it certainly doesn’t discourage algae.

 

Ready Patch

  • Ready Patch
    Ready Patch after 1 year

    Ease of Application: 3

  • Ease of Sanding: 2
  • Ready to Sand: 45 mins

Application: Ready Patch is very easy to apply though it had a little difficult time staying in the hole initially otherwise I would have given this a 1 or 2 in ease of application. It didn’t seem to want to stick to the wood at first but with a little extra pressure it did just fine.

Drying: It was ready to sand in 45 mins which was in the middle of the field for the fillers I tested. I think the longer dry time was due to such a large patch because when I use this regularly for small patches or nail holes it’s usually dry in a matter of minutes. This is not an epoxy so the larger the patch the longer the drying time will be.

Sanding: Was a cinch just like WoodEpox. Although be careful that it is dried all the way through if you do a large patch because the outside felt dry and firm long before the center was dry enough to be sanded.

Results: The first year was pretty tough on Ready Patch as I thought it would be. After sanding smooth it shrunk up considerably leaving a decent divot. That confirms with me that you’ll need multiple thin coats or only use it for small hole filling like nails. The patch began pulling away from the wood within the first few months and looks pretty gnarly at this point. There is a fair amount of algae growth as well.

 

KwikWood

  • KwikWood
    KwikWood after 1 year

    Ease of Application: 5

  • Ease of Sanding: 2
  • Ready to Sand:  25 mins

Application: It’s like cutting off a chunk of a tootsie roll and mushing it all together. Fun and easy though it does get pretty sticky as you keep mixing until both parts of this epoxy stick are blended. I’ve found it helps to have wet hands while mixing to keep this stuff from getting all over your hands. It is a fairly tough material and required a bit of force to get the hole completely filled, but it stayed in place very well and didn’t seem to have any bonding issues. There really isn’t a good way to smooth the surface of this before it’s dry because it gets very sticky.

Drying: Kwikwood dried super fast and very hard. In only 25 mins it was hard as wood and ready to be sanded.

Sanding: It sanded surprisingly well considering how hard it felt. Once finished it gave a nice smooth surface that if painted would blend in perfectly with the wood.

Results: I use Kwikwood a lot for quick spot repairs so I’m pretty familiar with it, but I was still surprised how well it held up. There was no shrinkage over the year and it had even less pulling away from the wood than the WoodEpox. Very minimal if at all. The thing that impressed me most was how it seems to be totally algae proof. Nothing would grow on this portion. The Kwikwood looks just as clean as the day it went in even though the surrounding wood is green and discolored. The only bad thing I’d say is the cost. It doesn’t seem like an affordable way to repair large portions of things like wood windows and the fast drying time while great for small pairs is not workable for a large reconstruction.

 

Minwax Wood Filler

  • Minwax Wood Filler
    Minwax after 1 year

    Ease of Application: 2

  • Ease of Sanding: 2
  • Ready to Sand:  50 mins

Application: Super easy to apply the standard stainable wood filler is not something I use often though this test has me reconsidering. The nozzle tip made it easy for small applications but for larger areas it was a lot of work to get the filler out. After a few uses the stuff tends to clog the tip and be more difficult to use as well.

Drying: 50 minutes puts this filler as the second longest drying required, but just like the Ready Patch the drying time greatly depends on the size of the patch you do.

Sanding: As expected it was simple to sand and left a smooth surface that has a little grit to it like the surface of the wood.

Results: I was honestly surprised by how the Minwax filler did. It did algae a little bit, but mostly it has held its own against the high end fillers and epoxies. Very little shrinkage and almost no pulling away from the wood. Time will tell, but for now well done Minwax.

 

Minwax High-Performance Wood Filler

  • MInwax High-Performance Wood Filler
    MInwax High-Performance Wood Filler after 1 year

    Ease of Application: 8

  • Ease of Sanding: 7
  • Ready to Sand:  20 mins

Application: This stuff stinks to high heaven and it’s a sticky, gloppy mess to apply, but once it’s in the results are pretty great. Make sure to wear gloves and have plenty of ventilation. It has a two part system that requires only a small amount of reactive agent (16:1) so it’s hard to tell if you’re using the exact right portions. Bottom line, you guess how much to put in which can make performance a little variable.

Drying: It says 30 mins on the can, but it was ready for me in 20 mins which may have been due to the high 80’s temperatures and high humidity when I did the test. Either way it was the fastest to dry of everything I tested narrowly beating out the KwikWood.

Sanding: I’m not going to lie that this filler seemed a bit resistant to sandpaper. It took longer to get a smooth surface than with all the other fillers, but it eventually gave a nice smooth finish.

Results: This was another epoxy that, like KwikWood, was completely immune to any algae growth which was nice. Over the year it didn’t start to move much until the last few months when one of the side joints between the wood and the epoxy developed a crack that is somewhere between the tiny size of the WoodEpox and the larger gap with the Ready Patch.

The Results

I don’t think this test will change much of what I use at the moment, but I’m curious to see how these fillers progress over the years or brutal exposure. My go to filler especially for window repair is still WoodEpox because of its strength and relative ease of use, but time may change that. I’m very loyal to whomever has the best product.

I believe all these fillers are meant to be primed and painted so while this isn’t exactly typical usage I figure that if they can stand up to these conditions they can stand up to anything.

I’ll keep you posted on how things progress year by year.

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13 thoughts on “The Wood Filler & Epoxy Test (Year 1)”

  1. Also helpful to note is that the WoodEpox is easier to apply if you dip your putty knife in alcohol. Keeps it from sticking to the knife and lifting out of the joint you’re filling

  2. Professional historic preservationist who are using epoxies all the time do not use these products with the possible exception of Abitron’s products which has a very mixed reputation. They use the West System and ART (Advanced Repair Technology).

    1. Bob, I am a professional historic preservationist, I have dozens of colleagues who use some of these products. You may like West System, but I do not. Please don’t speak of what you do not know.

  3. Hi Scott,

    Please take a look at Rot Doctor. I use their line of products and my only regret is that their epoxy system was not available when I bought my old house 30 years ago. Their epoxies are wood based, and more flexible than petroleum-based epoxies. One of the key components is the Clear Liquid Epoxy Sealer (CLER) that penetrates and solidifies soft wood, kills whatever unseen mold spores that may exist in intact wood, and serves as a ‘primer’ for the epoxy filler. I have not had any of the problems that you describe with Rot Doctor.

    I have no affiliation with Rot Doctor other than being a very satisfied customer.

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