Official Luthiers Forum! :: View topic - T-88 structural epoxy as a grain filler?

Don't do it.

That T88...given it's mechanical properties is going to be "toughened" epoxy....which means it formulated to have anti micro-cracking properties...which make it particularly hard to sand. It also means that mostly likely...denatured alcohol can't be used to thin it.

If you are pore filling with epoxy you will want to do a final wash coat at the end of the process to guarantee you've covered your sand-throughs. If you don't do that step you'll get blotches when top coating. You need an epoxy that you can thin with denatured alcohol without totally altering it's mechanical properties. Z-Poxy and Bob Smith Industries epoxies are the only ones I know of that allow 5 - 10% denatured alcohol without big changes.

Also...when buying either product...make sure it's "Finishing" epoxy. Both companies manufacture other stuff...and you don't want anything but the finishing epoxy for pore fill.

Author:	warpedbored [ Sun Feb 24, 2013 10:46 pm ]
Post subject:	T-88 structural epoxy as a grain filler?
I'm thinking of trying T-88 structural epoxy as a grain filler because it's thick and gives quite a bit of open time. The current build is ribbon figure Mahogany which is very porous. Anyone ever try it?

Author:	klooker [ Mon Feb 25, 2013 7:11 am ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Never used it but they describe it as non-brittle which makes me think it won't be easy to sand? Kevin Looker

Author:	Stuart Gort [ Mon Feb 25, 2013 11:44 am ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Don't do it. That T88...given it's mechanical properties is going to be "toughened" epoxy....which means it formulated to have anti micro-cracking properties...which make it particularly hard to sand. It also means that mostly likely...denatured alcohol can't be used to thin it. If you are pore filling with epoxy you will want to do a final wash coat at the end of the process to guarantee you've covered your sand-throughs. If you don't do that step you'll get blotches when top coating. You need an epoxy that you can thin with denatured alcohol without totally altering it's mechanical properties. Z-Poxy and Bob Smith Industries epoxies are the only ones I know of that allow 5 - 10% denatured alcohol without big changes. Also...when buying either product...make sure it's "Finishing" epoxy. Both companies manufacture other stuff...and you don't want anything but the finishing epoxy for pore fill.

Author:	warpedbored [ Mon Feb 25, 2013 2:09 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Thanks guys I'll try the Zpoxy. I have tinted T-88 before with alcohol based Transtint dyes but I've got too much time and work into this guitar to try something I'm not sure about. I did find some Zpoxy here on clearance for $10.99 if anybody needs some. http://www.miniaturemarket.com/pt-40.ht ... QgodEwsAiw

Author:	dzsmith [ Mon Feb 25, 2013 7:48 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Zlurgh wrote: Don't do it. That T88...given it's mechanical properties is going to be "toughened" epoxy....which means it formulated to have anti micro-cracking properties...which make it particularly hard to sand. It also means that mostly likely...denatured alcohol can't be used to thin it. If you are pore filling with epoxy you will want to do a final wash coat at the end of the process to guarantee you've covered your sand-throughs. If you don't do that step you'll get blotches when top coating. You need an epoxy that you can thin with denatured alcohol without totally altering it's mechanical properties. Z-Poxy and Bob Smith Industries epoxies are the only ones I know of that allow 5 - 10% denatured alcohol without big changes. Also...when buying either product...make sure it's "Finishing" epoxy. Both companies manufacture other stuff...and you don't want anything but the finishing epoxy for pore fill. Hi Stuart. Please clarify wash coat: Should the entire wood surface be coated with epoxy prior to finish or just the open pores? Thanks, Dan

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Author:	Stuart Gort [ Mon Feb 25, 2013 11:00 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
dzsmith wrote: Hi Stuart. Please clarify wash coat: Should the entire wood surface be coated with epoxy prior to finish or just the open pores? When you try to level the filled pores you'll be hard pressed to do so without sanding through the film and exposing fresh wood again. If you try to sand ALL the film back so that just the epoxy filled pores are left you'll open up unfilled pores. ou chase it either way. The easiest technique is to fill the pores, level almost down to the wood, and then apply thinned wash coats to get the areas that you sanded through to the wood.

Author:	dzsmith [ Tue Feb 26, 2013 7:18 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Thanks for the advice fellows. I planned to use transtint directly on wood and then pore fill, but this no longer seems feasible. I would no doubt sand through the fill into the color. I reckon I'll do some experiments to see what works. I've used transtint on bare wood before and like the ability to lighten and blend it. I'll stop here before I skew this thread further from the original post. Dan

Author:	warpedbored [ Sat Mar 23, 2013 10:41 am ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
Before I cut the binding and purfling channels I used Seal Coat shellac sanding sealer to firm up the fibers. Since then there are many spots on the guitar where I've sanded through to bare wood. Before I use the Zpoxy should I sand the rest of it down to bare wood or apply more sanding sealer first? Also I'm leaning toward a French polish finish rather than lacquer afterward. Suggestions?

Author:	meresing [ Sat Mar 23, 2013 2:14 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
`poxy grain filler??? Wouldnt use on ANYTHING unless its under a solid color! Once youve sprayed an adequate wash-coat/sealer coat... Apply your wood/pore filler over this and remove all of this excess. Let this dry for 24 hrs. Before flatagsanding and then apply 4 to 8 coats of your clear finish, (lacquer or poly). I like using clear shellac as a sanding sealer as it flows well and almost any finish coats will adhere to it very well. Every four to six coats (THIN) allow to dry overnite and flatsand before applying the following coats. It varies from maker to maker to maker and finish to finish but I like to end up with a final finish thickness of 5 to 7 thousandths... Wood needs to breathe and after a certain point, too thick a finish starts deadening resonance and tone.... Not to mention obscuring all that beautiful grain underneath we love and pay so much for! Stew-Mac has some excellent materials available on staining and finishing at inexpensive prices and Id recommend to anyone to get them.

Author:	Mike Dotson [ Tue Mar 26, 2013 5:54 pm ]
Post subject:	Re: T-88 structural epoxy as a grain filler?
While T-88 might not be the best choice (although I've used it successfully) as a filler epoxy in general certainly doesn't 'obscure the grain' and it doesn'tcause thick finishes. PS, wood doesn't need to 'breathe'....it's dead.

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