The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #1  
Old 11-19-2013, 08:07 AM
fazool's Avatar
fazool fazool is online now
Charter Member
 
Join Date: Dec 2012
Location: Buffalo, NY
Posts: 16,562
Default ColorTone Aerosol Nitrocellulose mini-review (long)

Nitrocellulose
------------------

Shellac was the standard and leading edge of instrument finishing technology throughout the 19th century. This was replaced by nitrocellulose, which reigned through most of the 20th century. Nitrocellulose:

- is flexible when cured, allowing free movement of an instrument's wood.

- is reasonably rugged and durable, bonding well to it's wood substrate and resisting chipping.

- is highly "workable" allowing for every possible degree of polishing, from matte to mirror-like super glossy.

- bonds to prior applications, allowing for repairs and touch-ups.

As a finishing solution, Nitrocellulose does have its weaknesses, however.

- It is susceptible to chemical attack, especially by vinyls and other plastics.

- It is nasty to apply, especially when spraying, with strong health and environmental concerns.

- It is a dangerously explosive substance, finding use in solid rocket engines.

- It is a very tedious process, requiring many applications for best results.

For the above reasons, the 21st century industry is heading toward nitrocellulose's successor, probably a polyester-base. This same shift is occurring in automotive painting which is another significant finishing industry.

Nonetheless, Nitrocellulose is still currently used and largely viewed as the "gold standard" of finishing by purists, especially for vintage instruments.

Often referred to as simply "nitro", Nitrocellulose finish is simply a lacquer "paint" made of tinted nitrocellulose, dissolved in lacquer thinner. Many lacquer paints are nitrocellulose based, although they are getting harder to find.

Nitro can be brushed on, however, it is really intended to be applied with professional-grade spray equipment. Recently, companies have developed aerosol can versions of nitrocellulose lacquer, marketed as musical instrument grade. ReRanch carries their own labeled brand. Mohawk Finishes advertises one. Stewart McDonald sells ColorTone brand.

I was advised by a finishing expert that the aerosol cans are mixed with more thinner, to help them spray out of an aerosol can's nozzle. This means that more thin coats will be necessary when using a spray can.

Imagine a hose-spray of water on your car hood - it collects in puddles because the surface tension pulls the liquid toward itself. Spraying lacquer can be like a microscopic version of that - the liquid will try to "pull itself together" creating puddles and voids.

Additives are mixed in, which reduce the surface tension, encouraging the liquid to level itself. Retarders can be added to slow the drying time, allowing more leveling to occur and allowing humidity to escape before getting trapped.

Lacquer retarder cannot be added to aerosol cans, so excess heat should be avoided. You don't want it to dry too quickly or moisture will be trapped, creating a milky haze/fog effect and you will get some orange peel effect when the surface doesn't have time to level.

If a lacquer coat is not fully cured it may be "skinned over" on top, but still soft underneath. Spraying a new coat will dissolve the top of the skin, bonding to it, but the whole skin is now pulled against the soft part below. This will also create an orange peel effect.


My refinishing project
-------------------------------

I am only mid-way through my 1980 Gibson electric restoration, detailed HERE but I wanted to share my experience with aerosol nitrocellulose. Photos are in that thread.

My guitar’s body was in fair-to-good shape, with some nicks through the finish to the wood. The neck had wear down to the wood in small spots.

The original Gibson specification listed a "gloss" finish. It was extremely smooth but only marginally glossy. Definitely not your Tuxedo or Baldwin grand piano glossy black.

I chose black nitrocellulose, with a clear satin nitrocelluslose on top. A trick I use is to apply a satin finish and then polish with carnuba wax, creating a fast slippery feel and a smooth barely-gloss finish.

The products I used were:
-------------------------

3M Bondo 1-part Glazing & Spot Putty from most auto parts stores. The product designations for these products are confusing, just make sure to get the 16 oz single-part tube (that comes only in a box). Do not get a blister pack or multi-part, or any other variant, even if it sounds the same. This is the only one that is appropriate - it is a nitrocellulose lacquer filler, so the nitrocellulose finish will bond to it and you will get even expansion and contraction rates (avoiding cracks).

ColorTone gloss black Nitrocellulose aerosol Guitar Lacquer from Stewart McDonald.

ColorTone satin clear Nitrocellulose aerosol Guitar Lacquer from Stewart McDonald.

Tester's Gloss Black modeling (lacquer) paint. This isn't listed in the procedure but was used in spots where i didn't want to spray black (like over the Gibson logo) or where I had tiny nicks and needed a microscopic drop fill.

Turtle Wax Scratch & Swirl Remover (aka Paint clarifier) from most auto parts stores.

3M flexible 3000 grit sanding pad from most auto parts stores. The grit rating is different than paper and this is similar to micro mesh sold in smaller pieces from Stewart McDonald.

Turtle Wax polishing lubricant for wet sanding. Plain water can be used for wet sanding, or you can make your own lubricant by adding a drop of dish detergent.

Naptha from most hardware stores.

Guitar Nomad carnuba wax guitar polish from Guitar Center.

3" foam pads and buffing wheels from Harbor Freight.



The process I used was as follows:
-----------------------------------------------
Most seem to recommend a few coats of color, followed be many coats of clear for a deep gloss. Since I am striving for a satin finish, I needed fewer clear coats.

Fully disassemble the body. Lightly wet sand the body with 1000 grit paper, removing surface contaminants and superficial scratches. Wipe the body with wet rags and fully dry.

Wipe the body down with naptha to clean any oils or dirt left behind. Allow the naptha to flash off fully.

Apply the bondo lacquer filler in thin layers to nicks, dings and deep scratches. Sand with 320 grit and reapply until imperfections are filled. Wet sand with 600 grit. Wet sand with 1000 grit.

Wipe the body down with naptha and allow the naptha to flash off fully.

Apply coat one of black nitro and allow to dry 3 hours.

Apply coat two of black nitro and allow to dry 3 hours.

Apply coat three of black nitro and allow to dry 24 hours.

Wet sand with 3000 grit micro mesh.

Wash the body and fully dry. Wipe the body down with naptha. Allow the naptha to flash off fully.

Apply coat four of black nitro and allow to dry 3 hours.

Apply coat five of black nitro and allow to dry 24 hours.

Polish with Paint Clarifier and medium speed foam wheel.

Wash the body and make sure the body is completely dry, gently using heat lamps and a hair dryer to eliminate ALL humidity and moisture.

Wipe the body down with naptha and allow the naptha to flash off fully.

Apply coat one of clear nitro and allow to dry 3 hours.

Apply coat two of clear nitro and allow to dry 24 hours before handling.

Allow to cure/dry for 5-7 days.

Apply heavy coat of Carnuba wax and allow it to harden under for 24 hours minimum.

Hand polish the wax removing heavy excess. Lightly polish wax by hand.

Apply light coat of wax and harden under (gentle) heat lamps for 2 hours.

Machine polish with medium speed cloth buffing wheel.


Notes and Comments:
-------------------

My "heat lamp" I is actually a $19 dual halogen tripod work light. They are great shop lights and project a lot of warmth. They aren't real infrared heat lamps, but they warm up their target nicely. When using these as "heat lamps" go for the feel of a hot summer day (not much more) so probably 90-100 deg F.on the surface.

When spraying, if you wear gloves, cut the finger tip off the index fingers of the gloves to avoid blocking the spray pattern.

Wear a good mask/respirator (not just a dust mask) and have plenty of ventilation.

The black nitrocellulose aerosol worked wonderfully. I was amazed at how well it worked. It went on evenly and covered well. It was very forgiving and evened out nicely. It's expensive - about $11 a can - but the highest quality aerosol I've used.

The clear nitrocellulose was a little more problematic. I did have some spitting from the can and that created a couple "strings" about 1 cm long. One of these knocked off once it dried and subsequent coats blended them in, but be aware of this. Its very important to start spraying off the work-piece and move onto it. That's always the method, but hold it off a second longer, especially with the clear.

I attached a holder to the bolt-on neck location for handling and let the parts hang to dry.

The nitrocellulose really levels out nicely over time. Even after the final coat, it continues to visibly level for a few days. Waiting for a few days for the finish to level and harden is your best strategy.

The 3000 micromesh was able to just break through two coats of black on the edges, so use caution when smoothing.

The swirl remover never broke through any finish - it was not aggressive at all. I used this with a medium-high speed drill attachment and foam wheel and polished a lot with this. I found this a better tactic - it was a safe non-aggressive method.

The swirl remover splatters everywhere! It also stains and bleaches clothing so wear old clothes.

If you have a small project and don’t have professional spray equipment, I can highly recommend the ColorTone aerosol nitrocellulose. I will be using it again on future projects.
__________________
Fazool "The wand chooses the wizard, Mr. Potter"

000-15 / GC7 / GA3-12 / SB2-C / SB2-Cp / AVC-11MHx / AC-240

Last edited by fazool; 11-19-2013 at 08:51 AM.
Reply With Quote
  #2  
Old 11-19-2013, 03:34 PM
fazool's Avatar
fazool fazool is online now
Charter Member
 
Join Date: Dec 2012
Location: Buffalo, NY
Posts: 16,562
Default Cost

I know this is an electric guitar project, in an acoustic guitar community but it might be interesting as one more point of reference.

I searched quite a bit and narrowed my list to a dozen well respected luthiers/shops for refinishing. I included a broad cross-section :
  • authorized manufacturer repair site
  • nationally renowned repair/restoration shops
  • original manufacturer's repair/restoration center
  • small local luthier
  • specialty restoration luthiers
  • referral to any of the above from any other of the above

For the refinishing of the body and neck, I got quotes that ranged from
$315 to $550, with quoted times from 4 to 8 weeks.

Most of the quotes seemed to come in around the $325-350 range.

So, if this is something your would consider having done, it might be worth the $25-$50 to try it yourself. In the worst case: you mess it up and have to get it redone by someone else, anyway.
__________________
Fazool "The wand chooses the wizard, Mr. Potter"

000-15 / GC7 / GA3-12 / SB2-C / SB2-Cp / AVC-11MHx / AC-240
Reply With Quote
  #3  
Old 11-20-2013, 12:52 AM
Sam VanLaningham Sam VanLaningham is offline
Registered User
 
Join Date: Nov 2012
Location: Bend, Oregon
Posts: 1,236
Default

Didn't happen without pics!!!!!

I used this stuff to do my first 3 electric bodies....I'll post pics tomorrow if you do
Reply With Quote
  #4  
Old 11-20-2013, 10:54 AM
SanzoneGuitars SanzoneGuitars is offline
Registered User
 
Join Date: Oct 2013
Posts: 38
Default works well but...

Great job on the process, very thorough. I've used the stew-mac cans as well, they are really user-friendly. No worries about water vapor, atomization, thinner/lacquer ratio, clean guns, etc. You are so right about the spitting, it can ruin your world. And the high solids/low pressure of the can take some getting used to. Handy option for the small shop. I like the preval sprayer, same low pressure but you can mix your own lacquer. Ever tried it?
__________________
Chuck Sanzone
sanzoneguitars.com
Reply With Quote
  #5  
Old 11-22-2013, 01:28 PM
redir redir is offline
Registered User
 
Join Date: Aug 2011
Location: Mountains of Virginia
Posts: 7,657
Default

I use the stew mac cans for touch up repairs like a broken head stock or something similiar and imo they work quite well.
Reply With Quote
  #6  
Old 11-24-2013, 10:06 AM
fazool's Avatar
fazool fazool is online now
Charter Member
 
Join Date: Dec 2012
Location: Buffalo, NY
Posts: 16,562
Default

pics of my project are in this thread

full pics here
__________________
Fazool "The wand chooses the wizard, Mr. Potter"

000-15 / GC7 / GA3-12 / SB2-C / SB2-Cp / AVC-11MHx / AC-240
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools





All times are GMT -6. The time now is 04:57 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright ©2000 - 2022, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=