Telegraphing of Epoxy Filler

Pros discuss ways to prevent epoxy fillers from telegraphing through finish coats. February 13, 2006

Question
I'm using an epoxy filler to fill countersunk holes and I would like to use white lacquer as my finish. After the lacquer has been applied the filled holes telegraph very clearly. We checked them after the sanding stage and the surfaces were as flat as glass. Can anybody help?

Forum Responses
(Finishing Forum)
From contributor A:
Did it shrink after the primer? If so, can’t you refill them again before the topcoat or primer again? Have you given the filler enough time to dry, and then sanded it after that? It always shrinks for me after filling a wide crack and I do fill again, sometimes up to three times. If it shrinks after the primer or basecoat I fill it again or just do some repairing after the finish topcoat.


From contributor B:
I've had a lot of experience in composite boat construction. Most boatbuilders refer to your situation as *print thru*". There are two major causes:

1. Using two materials side by side that have drastic differences in hardness (epoxy vs wood)
2. All plastic resins (epoxy, polyester, catalyzed varnish, etc.) take a very long time to fully cure. Polyester can take up to a year to fully cure.

It is much more obvious on large flat surfaces like boats and cars. On boats you can actually see the fiberglass cloth print thru 5 coats of epoxy paint and 1/16 of filler.


From Paul Snyder, forum technical advisor:
Are you using a primer/sealer? Two coats of a good primer that are level sanded between coats have always worked well for me to keep the fillers from re-appearing. I usually use Bondo or similar filler for larger holes and solvent based wood putty (Famowood) for smaller holes. Glazing putty works well for tiny cracks.

From the original contributor:
Thanks for the advice so far. Also, I'm trying to find the best way to finish furniture white - can anybody recommend a product that is user friendly? I hear a lot about white polyurethanes - is this the best way to get that white painted finish?

From contributor A:
I use a 2K poly and I would recommend using that over a white primer.

From Paul Snyder, forum technical advisor:
How would you define *user friendly*? For painted furniture, you have a number of spray finishes to choose from:

Water-base (waterborne)
Nitrocellulose (NC) Lacquer
Pre-catalyzed Lacquer
Post-catalyzed Lacquer
Conversion Varnish
2K poly

Depending on the selection your local suppliers have, you may have the option to use any of them. They all should have a primer/sealer available within the same brand.
Choose between them based on the properties you want:

Water-base (waterborne)
May or may not need a catalyst depending on the brand. A catalyst is used for improved durability and increases the health risks while spraying.

Nitrocellulose Lacquer
Moderate durability. Tends to yellow with time. Easy to use. Lower solids content requires extra coats.

Pre-catalyzed Lacquer
More durable than NC lacquer. Also easy to use.

Post-catalyzed Lacquer
Better hardness and/or solvent resistance than pre-cat. Must be catalyzed and used within a specified time frame (often 8-12 hours).

Conversion Varnish
Overall durability is better than any of the lacquers. Must be catalyzed and used within a specified time frame (often 8-12 hours). High solids content allows for fewer coats.

2K poly
Overall durability is better than conversion varnish. Must be catalyzed and used within a specified time frame (often 3-8 hours). High solids content allows for fewer coats.

They're all user friendly in my mind. What choices do your local finish suppliers have? What's wrong with the lacquer you're using? Are you using a primer/sealer?


From contributor D:

ML Campbell's Clawlock will help. Prime with that and your telegraphing problem should be over with. Scuff before applying topcoats. Clawlock is a post-catalyzed primer. Add 10% catalyst by volume. What's easier than that?

From contributor E:
If you properly mix the epoxy catalyst and the resin, the epoxy should not be affected by the solvent. If you are using the *tootsie roll* type, or the colored epoxy, then you need to knead or thoroughly mix the two parts until you have one uniform color throughout.
Use your finger nail to see if the epoxy is cured, before you apply your clear coats.
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