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I'm trying the z-poxy pore filling method for the first time on a rosewood dred copy. I used Michael's tip for using the foam makeup wedges (got em from Walmart) for applying the first coat and found that it's best not to swab it on too aggressively or the foam will start to ball up and deposit bits onto the surface. If that started happening I'd grab a new foam wedge to use.
I scraped the excess off with a razor blade am ready to sand and apply the 2nd coat.

My question is, what's a good grit of sandpaper to use between coats of the z-poxy? I sanded a little on the lower bout with 150 and that seemed to work OK. Could I go down to 100 grit without problems?

I usually get close to 100% of the pores the first go around. However,
sometimes I have just a few sporadic places that I didn't get.

Here is what I do:

I like to use the clear credit card thingys you get in the mail all the time.

I like to have the epoxy very, very thick. About the consistency of
petroleum jelly.

I do small sections at a time. The front...the sides...the back...the neck. I
always just work on one guitar at a time.

I use a spatula to deposit the epoxy in small "patches" that are evenly
spread out on the surface I am working on.

I then spread out the epoxy...making sure I spread the stuff from all
angles. You don't want to leave anything on the surface..just in the pores.

If it is done correctly...you should be able to get a surface that is close to
flawless. I touch up with a little 320 grit sandpaper. If you have a little
bump - use a cabinet scraper to knock it level.

Only with unusual circumstances, should you need to apply it more than
twice.

Once you get the hang of it...epoxy does a wonderful job.

Best of luck

Thanks for the advice, Simon and Terken. The z-poxy thickens fairly slowly so I'll try applying the 2nd coat at the thicker consistency and will try the bondo applicators too.
I haven't tried it yet, but there's a widely-available and inexpensive product that has the same consistency as epoxy, dries fast and sands well... the polyester resin used in automotive and boat fiberglass repairs. I have a jar of amber-colored stuff that might work well for pore-filling so I'm gonna experiment on some scrap mahogany later this week and see what happens to it under nitro. The polyester resin can be found at any Walmart or auto parts store.

The problem with letting it thicken is that it may bridge as apposed to fill the pore. What makes Zpoxy a great filler imo is the low viscosity allows it to run into the pores and fill from the bottom up as it were. If it gets thick is is setting and may bridge some pores vs. filling.

I like it thin so I can sand back to the wood with confidence that the pores are filled.

The main difference in a finishing resign and a slow set epoxy is a finishing resin has a low viscosity that allows it to self level better. So if you thicken it you could have used a med viscosity epoxy, though it may not sand as well.

Buddy Lee you are right you don't want to press to hard or the foam will fall apart. I use a new pad pretty often so that this does not become an issue.

I have used the credit card or squeegee method for most of my work, the foam pad is a new technique

Michael has an excellent point - you don't want to let the epoxy thicken
with time (i.e. start to harden) and then spread it. I make the epoxy
thicker by adding silica. I actually find that a thicker consistency allows
the pores to be filled much, much easier. I have always used System 3
epoxy so I really can't comment on any other epoxy. Assuming you don't
take forever, the thicker consistency epoxy is every bit as easy to remove
from the wood surface. I have used the epoxy at a less viscous state and
can only see positives to making it thicker.

I do tend to move pretty quickly and only refine myself to one surface per
"batch". The epoxy gets tacky as time progresses - I imagine if you take
too long it can actually pull itself out of the pores. After everything is
filled, I like to take a flexible credit card and scrape the surface down very
well, removing any excess epoxy from the surface.

It might be a slighlty different approach than some take - but I really do
find that the epoxy works better if made a bit more viscous.

Many different ways to accomplish the job - ultimately, do what works
the best for you.

God bless,
Simon

I've not used the type of epoxy you mention, but have had great success heating epoxy prior to use.
I go through quite a bit for inlays, and a few minutes before I'm ready to mix, I put it in front of an incandescent lamp.( I use devcon 2 part 5 minute clear epoxy).
Heating it tends to thin it out, which makes it easier to mix, including mixing in powdered analine dye, and also seems to allow trapped air to release quickly.

I'm wondering if it might help in this process? I have found that it does fill any gaps much better using it this way.

_________________
Paul Bordeaux
http://www.bordeauxinlay.com

Just to play the devils advocate here. My argument about thick vs. thin is" the thinner or less viscous the epoxy the easer it finds its own level like water and the deeper into the pore it will flow. The dis-advantatage is you may have to fill more than once to level out to the wood outer surface but you can sand a bit in to the wood and still have the pore filled.

The thicker or more viscous the epoxy, the more likely the epoxy is to bridge the pore in stead of fill the pore.

It all boils down to surface tension. If the force needed to overcome the epoxies surface tension is higher than the pull of gravity on the epoxy then there is a greater chance of bridging the pore. Now I know we force the epoxy in under some pressure when we squeegee of rub the epoxy in but many pores are small and it is very easy to assume they are filled but in truth they are only part filled by bridging epoxy.

If I can be proved wrong I will gladly stand corrected.
MichaelP38859.5343981481

Michael, as a person with a strong background in biochemistry - I don't
think surface tension is really a factor. I think it really comes down to
what works best for the individual - I prefer thicker epoxy and seem to do
a better job with it. I feel like I can really push the epoxy into the pores
easier if its more viscous.

But you have far more experience than I - it could be I have just been
lucky the last few times. Normally I just let the more experienced speak
but since I have had such I good results with making the epoxy the
thickness of petrolatum - I thought I would share my thoughts.

There are many different ways to skin a cat - Ancient Chinese
proverb

[QUOTE=SimonF]I do small sections at a time. The front...[/QUOTE]
The front?

So, guys...have I been misunderstanding this all along? Are you all actually using epoxy glue to fill pores, and not finishing resin?

Really boils down to if you find your self sanding back past the original wood surface ever. If you thicken it up so that it may not push in to the pore full depth (which varies from wood to wood) then as long as you never sand past the origininal surface depth than it is a moot point anyway. But it never fails that I go through the outer film of epoxy in a few places so I like having the the insurance.

[QUOTE=CarltonM] [QUOTE=SimonF]I do small sections at a time. The front...[/QUOTE]
The front?

So, guys...have I been misunderstanding this all along? Are you all actually using epoxy glue to fill pores, and not finishing resin? [/QUOTE]

No not adhesive epoxy, though some do. but rather finishing resign. It is an epoxy top coat for the fiberglass industry. Adhesive epoxy tends to not harden as much and therfore not sand as well. Finishing resign is designed to be a hard sandable film that can be polished sanded. When we refer to zpoxy or system 3 we are speaking of a finishing resin.

Finish resin can be used as an adhesive but it is more britel in the shear strenght but that comes from being a harder film.MichaelP38859.7344907407

I use System 3 epoxy resin - I buy from LMII. I'm not an expert on this
stuff but I do believe it is an actual epoxy glue that has been modified to
have characteristics more useful for a pore filler.

If you use it correctly, the glue should just be in the pores. You shouldn't
end up with an actual "layer" over the wood. In principle, this is no
different than folks using hideglue to fill the pores. I think a lot of
individuals are starting to use epoxy as a pore filler because it can give
you an excellent results.

Some of us like to be sure ther is a micro thin layer on the wood to add color inhansment to the wood but we are talking micro mils not mils.

System 3 is a finishing resign the main differance in a finishing resin and an general adhesive resign is the viscosity and final film hardness. A finishing resin will be harder and have a lower viscosity.

[QUOTE=MichaelP]No not adhesive epoxy, though some do. but rather finishing resign.[/QUOTE]
Whew! Thanks, Michael. The way this thread was reading, it looked like folks were using the glue. I think it should be made clear to newbies that they shouldn't grab hardware store epoxy and start filling their pores.

[QUOTE=CarltonM] [QUOTE=MichaelP]No not adhesive epoxy, though some do. but rather finishing resign.[/QUOTE]
Whew! Thanks, Michael. The way this thread was reading, it looked like folks were using the glue. I think it should be made clear to newbies that they shouldn't grab hardware store epoxy and start filling their pores. [/QUOTE]

Um, no, it shouldn't.

I've seen far, far more people who use simple Devcon 5 minute epoxy or similar with good success than those who use finishing resin, or System 3.

Just FYI.

Mattia

[QUOTE=Mattia Valente] [QUOTE=CarltonM] [QUOTE=MichaelP]No not adhesive epoxy, though some do. but rather finishing resign.[/QUOTE]
Whew! Thanks, Michael. The way this thread was reading, it looked like folks were using the glue. I think it should be made clear to newbies that they shouldn't grab hardware store epoxy and start filling their pores. [/QUOTE]

Um, no, it shouldn't.

I've seen far, far more people who use simple Devcon 5 minute epoxy or similar with good success than those who use finishing resin, or System 3.

Just FYI.

Mattia[/QUOTE]

Like Mattia I use Aroldite 5 minute epoxy to pore fill - I'm just interested to fill the pores rather than coat the wood surface. Seems to work fine.

I bought some Z-poxy from LMI but am a bit concerned that it colours the wood - amber tint is used to describe it a lot - so I'll be checking it out on some scrap to check for the clour and that I can just get it in the pores and not on the wood.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Couple final thoughts here:

Adhesive epoxy for fill?
The four things that 5 min and 20 min epoxies have going against them is pot life, viscosity IMO, cured hardness and yellowing with age. The first two are not big issues but the last two will mean, first it will not sad near as well as a finishing resin, second it may yellow with age. I know many use them all the time and I have no issue with there pore filling properties but choose a good one that will not yellow. Most of the off the shelf or no-name 5 and 20 min. epoxies will discolor with time.

Will Zpoxy change the color of wood?
It will tint the wood about the same as a 2# cut of 50% amber/50% extra blonde shellac. I have used it on everything from Maple to Ziricote and none have displayed unwanted color changes. In fact IMO it only makes the natural under finish color pop a bit more. Also as I stated above, most off the shelf clear epoxy mixtures tend to yellow with time and UV exposure. Most finishing resins are designed not to yellow from ambient UV exposure. So if you use a clear off the shelf no-name epoxy because you don't want to affect the color be aware that with age if you left the epoxy on the wood (not just in the pores) that it is likely to yellow with age.

Last
There are clear UV resistant epoxies out there. But the off the shelf in your brick and mortar hardware store varieties are not likely to provide this UV resistance.
MichaelP38860.3912037037

Michael,

I hear what you say, and I will be testing out the Z-poxy on some scrap pieces.

What makes epoxy yellow with age? Is it exposure to light (including U/V) or to air? If the former, then even if it is just in the pores and not on the wood it will still go yellow. If the later then the covering of shellac/nitro ot whatever should stop this.

What in the finishing epoxies stops the yellowing with age that is not in the other epoxies?

Mattia,

What's the oldest finish you have that was done this way and does it show any signs of yellowing? My oldest is only about 5 months or so.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Dave: I've only done scraps/tests with any epoxy fill, been using waterbased stuff up until now, but I've read plenty of '5 minute epoxy used here' comments on various other forums. I've got some System 3 here that I'll be using, since it's actually about as expensive as Araldite, etc. is locally.

Dave I believe it is a combo of things. The chem. reaction in its self of most quick set epoxies tend to yellow pretty quick due to the heat build up at cure. The faster an epoxy cures the more heat generated by the chemical reaction. And they are also yellowed by UV rays. So yes it happens in the pores as well to some degree. I personally don’t think anything will stop this and I know of no UV inhibitor to add to shellac or lacquer top coats that would for sure eliminate it.

Finishing resins on the other hand are slow set epoxies. So there is less heat build up during curing plus they have UV inheritors and are a harder film after cure. Remember this finishing resin is designed to be a top coat final film on fiberglass products. A gel coat that you put on a fiberglass boat is a finishing resin. So it is formulated to be a weather and element durable finish.

If you have doubts about clear, off the shelf 5 or 20 min epoxies yellowing just mix a small batch spread it on some glass and let it cure then look at the color. Now set it exposed to the sun for 48 hrs. You may be shocked in both cases
MichaelP38860.4678009259

Depending on the graphics card on your computer these look a little redder than in real life I am guessing. the best way to describe the color imparted by Zpoxy is just a very-very light shade of amber added to the normal wet color of the wood. Barely enough to see.

Dave is doing the exact correct thing in testing it on various species of wood. Because no matter what anyone tells you till you see it, you just don't know.

I have tried several types and brands of epoxy and finishing resins. I prefer Zpoxy. Some like to use West Systems others System 3 but no mater what brand is your choice, I believe you will find that a finishing resin will out sand and out fill the dickens out of most any other epoxy or cream fill system.

Now....go clog some pores