Official Luthiers Forum!
http://www.luthiersforum.com/forum/

Why don't pores fill?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=25566		 Page 1 of 2
Author:  Pat Hawley [ Tue Jan 19, 2010 8:43 am ]
Post subject:  Why don't pores fill?
I'm currently filling the pores on #10 and I have to say that this step always tries my patience. I'm up to four coats of z-poxy on the back and still there are some pores not filled. Last night as I was applying the fourth coat, I could see that they weren't filling even though I was going back and forth over them in all directions right up to where I couldn't move the z-poxy around any more. They are like little black holes. I'm probably down to less than 50 still visible and now I'm thinking of drop filling them one by one. Any other suggestions?

Thanks,
Pat
Author:  Michael Dale Payne [ Tue Jan 19, 2010 8:53 am ]
Post subject:  Re: Why don't pores fill?
What wood? You likely know this but don't just move the Zpoxy around you need to use some effort to squeegee it into the pores. At a diagonal angle to the grain direction does the best job. If you use no force at all and just move the Zpoxy around the Zpoxy bridges the pore rather than fills it and as it sets it shrinks back into the pore. But I have to say 4 coats is a lot even for very porous woods like IRW
Author:  Hesh [ Tue Jan 19, 2010 8:57 am ]
Post subject:  Re: Why don't pores fill?
Hi Pat - I had a lot of trouble filling pores too with Z-Poxy, System III, and West Systems epoxy until I determined that you just can't squeegee the epoxy around in all directions and get good results or at least I couldn't...

The problem was that the pores would not fill - just as you are describing.

The Ah Ha moment for me was when I learned to not just use the card or what ever you use to do a squeegee action which is designed to spread and remove but instead use the card to "mash" the epoxy downward into the pores and only do the squeegee action once the pores are filled and to remove excess epoxy.

I mash the epoxy downward and from all directions and I have yet to not be able to fill all pores in two coats. Also these days I believe that I want finish on my guitars and not epoxy (except for the pores) so I am no longer leaving a thin layer of epoxy on the surfaces to pop the figure and color. Not saying that there is anything wrong with leaving epoxy all over your guitars - I just don't want to do it.

Here is a link to how I epoxy pore fill and you will see the mashing technique described: http://luthiersforum.com/forum/viewtopic.php?f=10117&t=20320
Author:  Hesh [ Tue Jan 19, 2010 8:58 am ]
Post subject:  Re: Why don't pores fill?
Michael explained what I wanted to explain with the idea that the epoxy "bridges" the pores and does not fill them.
Author:  Corky Long [ Tue Jan 19, 2010 9:04 am ]
Post subject:  Re: Why don't pores fill?
Hmmm - that sure does sound like something is awry. I've managed to fill all pores with two coats on walnut and Koa - perhaps the wood you are using is more challenging. What wood are you filling?

There's a great toot on filling with Zpoxy - actually two I think - Hesh put together one which I found very useful, and I think Robbie O'Brien also has a very useful one.
Author:  Pat Hawley [ Tue Jan 19, 2010 9:49 am ]
Post subject:  Re: Why don't pores fill?
Thanks for the replies. The wood is Indian Rose Wood. I have read Hesh's tout and thought I was "mashing" the Z-poxy but I still get pores left over.

Pat
Author:  Michael Dale Payne [ Tue Jan 19, 2010 10:07 am ]
Post subject:  Re: Why don't pores fill?
Lots of IRW does not have pores it has caverns. I found that best result came from working approximately 2” x 2” areas at a time with a very stiff credit card or actually I preferred a box cutter razor blade with the corners rounded. I also scraped off all excess. Once I had the surfaced worked one time I scrape off all excess, allowed to cure and lightly sanded to wood the repeated. On IRW that had really open pores it some times took 3 session or more. Leaving a noticeable film thickness on the surface I found made it harder to find the pores that were not filled from the previous session. Many fill session is just the nature of the beast when dealing with a very open pore wood like IRW.

This is also one of the reasons I swithed to med viscosity CA for 90% of my pore filling.
Author:  Mike OMelia [ Tue Jan 19, 2010 10:15 am ]
Post subject:  Re: Why don't pores fill?
I have been wondering about this. Just like CA, the thinner it is, the better it wicks. Perhaps thinning expoxy may make a difference (for first coat) since it should wick in better? I know Hesh knows what he is talking about, this is just a thought. Since the pores can effectively be pockets, mashing the stuff in could compress a little air, then bubble back out pushing the epoxy out? The tackier the stuff is, the less likely it will come out. Conversely, the same would be true if it was self wicking. I will do some experiments later.

Mike
Author:  Ken Franklin [ Tue Jan 19, 2010 10:26 am ]
Post subject:  Re: Why don't pores fill?
In the archive there's a post about heating the epoxy which makes it wick in and then using the squeegee. I haven't tried it but it might help.
Author:  Michael Dale Payne [ Tue Jan 19, 2010 10:27 am ]
Post subject:  Re: Why don't pores fill?
Actually medium thick CA (what I use to fill pores with) is very near the same viscosity of 1:1 Zpoxy but creates less surface tension until it starts setting. I do not recommend using thin CA as it is hard to control where it is going. I have not noticed air bubble issues when working Zpoxy just bridging then shrink back as it cures.
Author:  Hesh [ Tue Jan 19, 2010 10:30 am ]
Post subject:  Re: Why don't pores fill?
Just to check this one off the list there are Z-Poxy products that are epoxy glues and not "finishing resins." Although epoxy glue can work too as Mike says the thinner the better when trying to get it in pores and finishing resins, both Z-Poxy and System III finishing resins, are thinner than glue typically.

Usually the first coat fills the pores part way and when sanded back you see shiny spots. The second coat fills the pores to a level equal with the surface and the shiny spots go away when sanded back.

As Michael said just try to go in all directions with 45 degrees being the best direction to not strip the epoxy right back out of the pores.

On another note what color is your Z-Poxy - perhaps it is old?
Author:  Pat Hawley [ Tue Jan 19, 2010 10:40 am ]
Post subject:  Re: Why don't pores fill?
Just to confirm that I am using the Z-Poxy finishing resin. It's about one year old.

Pat
Author:  woody b [ Tue Jan 19, 2010 10:47 am ]
Post subject:  Re: Why don't pores fill?
If you sand too hard, or too much you may be sanding into new pores.
Author:  Hesh [ Tue Jan 19, 2010 11:09 am ]
Post subject:  Re: Why don't pores fill?
Pat bro even though I have a glove on better suited for a Proctologist than for working with epoxy you can see that I am not using the card to skim or squeegee the surface. Instead and for lack of a better word I am mashing the epoxy downward in the pic. That is the key to how I pore fill. In the past my results were as you are describing your results - not good and it was horribly frustrating until I learned to mash the epoxy.

The term "squeegee" was misleading to me in as much as I took it as a verb thinking that I want to use the card to scrape the epoxy off. Although this is true once the pores are filled first you want to get it into the pores.

Image
Author:  WaddyThomson [ Tue Jan 19, 2010 1:38 pm ]
Post subject:  Re: Why don't pores fill?
Hesh, do you make your guitars bend over for pore filling? wow7-eyes
Author:  Pat Hawley [ Tue Jan 19, 2010 3:21 pm ]
Post subject:  Re: Why don't pores fill?
I'll try to mash harder.

With respect to sanding through and opening new pores - is this easy to do, and, if so, how does one sand back to the point where epoxy is just left in the pores on one hand but no new pores have been opened up on the other. Sounds pretty tricky to me.

Pat
Author:  woody b [ Tue Jan 19, 2010 4:17 pm ]
Post subject:  Re: Why don't pores fill?
Pat Hawley wrote:
I'll try to mash harder.

With respect to sanding through and opening new pores - is this easy to do, and, if so, how does one sand back to the point where epoxy is just left in the pores on one hand but no new pores have been opened up on the other. Sounds pretty tricky to me.

Pat


For me it's hard not to open new pores, with some woods. Lightly sanding would help, but I get in a hurry and use too much pressure. My prefered method of pore filling is to spray a coat of sealer, either, vinyl sealer, rosewood sealer, or shellac, depending on which finish I'm using. Then fill with CA. It helps (at least it helps me) when sanding, and keeps me from sanding into new pores. After the pores are filled, I'll spray another coat of sealer, and then finish. I don't think (but don't know for sure if) epoxy can be applied over any of these sealers.
Author:  Hesh [ Tue Jan 19, 2010 4:21 pm ]
Post subject:  Re: Why don't pores fill?
Pat I don't find it easy to sand/pull the epoxy out of the pores. If you look at my toot I am sanding by hand and using a ROS and it stays in the pores.

How long are you waiting for it to cure because if you attempt to sand too soon it will clog paper and rip out of the pores.

Another thing to check off my list of things to check off my list... :) is if you shellaced the wood prior to using epoxy that would explain your issues. Epoxy does not stick well to shellac but shellac will sit on top of and stick to epoxy fine.
Author:  Pat Hawley [ Tue Jan 19, 2010 4:28 pm ]
Post subject:  Re: Why don't pores fill?
Hesh, I don't think this is about pulling out epoxy that is already in place but sanding down and opening up brand new pores. Not sure how you could tell a new pore from an old pore - I guess a brand new pore would have zero expoxy in it.

Pat
Author:  Howard Klepper [ Tue Jan 19, 2010 5:39 pm ]
Post subject:  Re: Why don't pores fill?
I don't use Z-poxy, which apparently is what everbody here uses. I use devcon 5 minute from the hardware store, and never have had to fill more than twice.

Two things re the OP's technique: (1) I squeegee with a dulled, corner softened single edge razor blade; (2) do NOT keep pushing your epoxy around until it has set up so much you can't push anymore. At that point you are pulling it out of the pores. Do press fairly hard with your squeegee ("mash" is not a word that comes to mind here), but when you feel the epoxy starting to set up, you should quickly (I don't know what this means with Z-poxy. With my product it means in the next 20 seconds or so) finish your squeegeeing, and stop well before the stuff stops spreading.

I work with the grain; probably not necessary, but I see no reason to change anything.
Author:  Hupaand [ Tue Jan 19, 2010 5:52 pm ]
Post subject:  Re: Why don't pores fill?
Is there an ideal grit sandpaper to use before you fill pores?
Author:  Mike OMelia [ Tue Jan 19, 2010 7:52 pm ]
Post subject:  Re: Why don't pores fill?
Lots of good tips here!

But I have to ask... why would shellac stick to epoxy, but epoxy not stick to shellac? We are talking de-waxed shellac of course. If one does indeed see this, might it be because the expoxy likes bonding with wood fibers better?

Where I notice pore filling problems the most is on curved surfaces (sides of the guitar, in convex bends). I bet more than a few share this observation. I can't help thinking this is a "mechanical" problem.

Mike
Author:  Hupaand [ Tue Jan 19, 2010 7:56 pm ]
Post subject:  Re: Why don't pores fill?
This 'mashing' business, is it true for all kinds of filler, or does it somehow apply mostly for epoxy?
Author:  Dave Fifield [ Tue Jan 19, 2010 8:58 pm ]
Post subject:  Re: Why don't pores fill?
Unfilled pores in EIRW is an issue I've been having lately too. On my latest guitar, I had to sand the finish back to wood and start over because I'd missed a few. I use Z-Poxy finishin resin with a squeegee that has a 6" handle. I thought I'd done the mashing well enough. Hesh's revelation that it might be the epoxy not adhering to an undercoat of shellac is more than likely what my problem is. Pretty much all of the pores I've had that don't fill have been around the edge of the guitar back. I always brush on a coat of shellac around the edge before I route the binding/purfling channels, so that must be it!

So, what's the answer? Not to use shellac to stiffen up the fibers so they cut cleanly during binding/purfling channel routing? Use vinyl sealer instead? Pore fill before routing the binding/purf channels? What?

Oh yeah, another related issue. How do you get the white powder (from the sanded epoxy coat/s) out of the pores that weren't quite filled? I've tried Naptha - that seemed to work on some of them, but not all. I have resorted to using a stain pen to disguise the white dots.....not an ideal solution at all. Any ideas?

Cheers,
Dave F.
Author:  Mike OMelia [ Tue Jan 19, 2010 10:28 pm ]
Post subject:  Re: Why don't pores fill?
Dave, this shellac thing is very interesting to me as well. Your comments/experience are very revealing. I think I will avoid shellac as well. I use high pressure air to blow off the dust (80+ psi). Then, a damp rag and I don't stop till all the residue is gone. If the epoxy is fully hardened, I don't see why it would not blow out.

Mike
Page 1 of 2 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/