Drop fill repair question

**bob77362** · 04-23-2019, 09:02 AM

Hello all.
I've done about a half dozen drop fill minor repairs on my guitars, and they've come out great. I prefer to use nitro, not super glue, even on a poly finish. My question is regarding the razor blade technique of shaving off the excess. I have been using a good quality scotch tape on the blade, but it wears too quickly. Once it even lightly marred the finish, when it wore through. I was thinking about using electrical tape, but it maybe thicker.
Any ideas on an alternative, or maybe a better technique? I could go directly to wet sanding, but it seems right to use a blade to have a level, head start.
Thanks, Bob.

**Grez** · 04-23-2019, 09:27 AM

My experience matches yours. The tape on a blade makes for a temporary tool. You just have to remake it from time to time.

TH · 04-23-2019, 10:22 AM

Just a two cent chime in. I use a curved scraper to level very localized areas, then I polish using very fine polishing pastes and buffing pads.
The scraper I use is one Luthier Al Carruth invented. As it's very sharp and has a compound curve edge, you can choose how sharp a line you want to level. I can get it to level flat a single line of a repaired crack, it's that accurate.
The polishing pastes I use are ones designed for the plastic modeling hobbyist. Tamaya three grit tubes with applicators. They polish so fine that you can remove any visible scratches from a clear plastic airplane model canopy.
Finally I seal it with a liquid wax that contains carnuba. That gives a uniform gloss and it protects from UV.
I've had good success with this system. By the way, you can get the scrapers from Al or StewMac, the pastes are easily bought on Amazon and the liquid paste wax is anything from Turtle wax to stuff I get in a bottle from Guitar Center.

David

**bob77362** · 04-23-2019, 11:19 AM

Thanks David. I'll check it out.

**neatomic** · 04-23-2019, 08:11 PM

good thing about super glue is that it dries and stays neutral colored...nitro might not..especially on poly body..it yellows at a different rate than poly

had good results with painters blue tape..good thickness...& comes off easy when time to replace too...

other tip is, don't get carried away with your fill...don't flood it...you don't want to have to scrape too much...better to go back a second time, than go overboard initially...if you get the actual drop right, the scraping and the sanding steps are way easier...and reduces chance of missteps

cheers

ps- classic primer by the great dan E

TH · 04-23-2019, 08:55 PM

Originally Posted by neatomic

good thing about super glue is that it dries and stays neutral colored...

How do you keep from bringing out witness lines when sanding back? It's the one reason I shy away from the use of cyano as a filler, it seems to leave a white line along the boundry of any area it's applied in my experience.
I have begun experimenting with various epoxies and acrylic dyes to colour the epoxy. A little blending of the artist's palette and the binary medium. I'll let you know how it turns out.
David

**neatomic** · 04-23-2019, 09:38 PM

david-

i think application temperature and drying time have impact...the slower the better..also must let it cure thoroughly..before scraping/sanding...if you have to get a guitar back to a client tomorrow, the results might be compromised compared to what might be done in a weeks time..it's unfortunate that repair turnaround times can compromise the craft

& not saying other fill mediums are not better or equal, or should not be pursued..but cyano has its merits...

just not crazy about nitro fills on poly idea!!

lastly, i have done aged/weathered olympic white fenders with cyano...tough color!!..(as they age into all sorts of color permutations)...and while at first there may be some slight discoloration, within a months time, between sunny room and case, the fill blends into obscurity..

cheers

**Bill Eisele** · 04-24-2019, 04:24 PM

Originally Posted by TruthHertz

How do you keep from bringing out witness lines when sanding back? It's the one reason I shy away from the use of cyano as a filler, it seems to leave a white line along the boundry of any area it's applied in my experience.
I have begun experimenting with various epoxies and acrylic dyes to colour the epoxy. A little blending of the artist's palette and the binary medium. I'll let you know how it turns out.
David

I’m in the process of doing a drop fill with StewMac’s amber colored cyanoacrylate. I hope that it more adequately hides those witness lines than the clear stuff. This is a revision to trying to do the drop fill with colored lacquer where too much color built up in the dent and it looked too obvious. Unfortunately the revised area is larger than the original dent and I’m not happy about that but will be patient and wait several days before scraping back the fill and buffing.

I will let you all know how it goes.

**bob77362** · 04-25-2019, 08:03 AM

If you sand through the finish due to a thin clear layer, what are your remedies? Just add to build up and re-sand? How do you get a level finish? Assume I don't have an air brush.

**Bill Eisele** · 04-26-2019, 12:19 AM

Originally Posted by bob77362

If you sand through the finish due to a thin clear layer, what are your remedies? Just add to build up and re-sand? How do you get a level finish? Assume I don't have an air brush.

Aside from having to match the tint of the bare wood with stain, would it be reasonable to spray using an aerosol can of a compatible finish material? Masking off just outside the repair area? And, then leveling using finer grits of an abrasive material like micro mesh and finishing off with abrasive compounds and polish? I have no experience with this, so just thinking about how I would approach it faced with the same situation. Here’s Dan Erlewine talking about using lacquer aerosol cans:

Dan Erlewine's 5 Tips for Aerosol Guitar Lacquer - YouTube.

**Bill Eisele** · 04-26-2019, 02:00 AM

And, here’s Dan Erlewine describing how to blend new lacquer into old lacquer over a drop fill repair using flash coats:

**Bill Eisele** · 05-02-2019, 05:46 PM

Originally Posted by Bill Eisele

I’m in the process of doing a drop fill with StewMac’s amber colored cyanoacrylate. I hope that it more adequately hides those witness lines than the clear stuff. This is a revision to trying to do the drop fill with colored lacquer where too much color built up in the dent and it looked too obvious. Unfortunately the revised area is larger than the original dent and I’m not happy about that but will be patient and wait several days before scraping back the fill and buffing.

I will let you all know how it goes.

It didn’t go well.

Not sure exactly why, but the guitar is now with Pete Moreno in Kalamazoo. I guess the lesson learned here is to know your limits and respect them. I didn’t want to make a poor repair any worse than it already was. I’ll report back when the guitar has been returned.

**bob77362** · 05-03-2019, 06:14 AM

That's too bad Bill. Do you have any before pics?
I'm binging mine to a local pro. I'm OK doing simple fills, but if it requires spraying, better to have someone with all the tools take care of it.

**Bill Eisele** · 05-04-2019, 12:34 AM

Originally Posted by bob77362

That's too bad Bill. Do you have any before pics?
I'm binging mine to a local pro. I'm OK doing simple fills, but if it requires spraying, better to have someone with all the tools take care of it.

I have photos that I’m attaching that show my first fill attempt that looks fairly close to what it looked like before the fill and what it ended up looking like. What was disappointing in the last attempt is blue tape that I used to mask the area pulled up some of the finish and created another problem. The original problem was someone had used a dark stain on the dent and I should have found a way to lighten it before proceeding with the initial drop fill. And, even though I didn’t get below the finish during the second go around except where the blue tape pulled up the finish, the color underneath seemed to move. Very strange. Oh well!