Official Luthiers Forum!

any experience with pre cat nitro?

i guess not

sure...a gallon can I have in my garage states 3 coats maximum....sounds like it is NOT suitable for instrument work if one wants to build up coats...

Depends on whose pre-cat. Chemcraft makes a fully two part catalyzed, and a pre cat nitro, and I know builders who are using both of those products with great success. For years, Larrivee used a Chemcraft poduct called Sadolin, I think it was referred to as a conversion varnish.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

I used it on my first three guitars. The oldest is only 4 years now, so I can't speak to how well it will
hold up for the next 50. But it went on (spraying) very well- so well I've used my last one for almost two
years without feeling the need to do the final polishing-out. It's hard, and did polish well (after a minimum 7-10
day wait) on the other two. I'm going to try french polishing on the one I'm building now, but if I have
problems, I'll be going back to pre-cat. I do think you will need to watch the production dates. Don't use
one that gets too old in the can.

_________________
Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Number of coats in irrelevant. It's all about final film thickness. I use Sherwin Williams products, including their hi-solids pre-cat. Don't exceed the 5-6 mil film thickness and you're good to go.
It's ready to sand the next day and ready to buff in 2.
Be sure to catalyze your sealer if you use a catalyzed topcoat.
Conversion varnish is not the same product. Great finish, but it won't "Burn in" if you need to touch up.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

Conversion varnish or Pre-cat nito?

Corrected punctuation:
Conversion varnish is not the same product, great finish, but it won't "Burn in" if you need to touch up.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

Interesting!!!!! So what is the typical catalytic agent in Pre-Cat Nitros. Say Sherwood Williams hi solid.

The catalyst is an acid. I don't know how the chemistry works, but it does.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

I have used ML Campbell's pre-cat MagnaLac on a few guitars. It builds much faster than regular nitro. 3 coats in one day and you are done, except for when you screw up and sand through. The factory says to sand between each coat, but I found that to be not necessary if recoated within an hour. Actually I have recoated at longer intervals than that without witness lines showing up. It is not a "miracle" finish like cat urethane or polyester - I do not find it to be much harder than regular nitro, and it still shrinks for quite a few days. Bottom line for me: a bit faster than regular, while keeping lacquer's repairability and ease of spraying. But if you are already set up to spray lacquer safely, and are looking for something better, I would look at urethane or polyester.

Brook

I don't mean to hijack this thread, but on the topic of ML Campbell's MagnaLac, I have a question for Brook. How long do you normally let it cure after your last coat before rubbing it out? I just finished spraying my last coat tonight on my second guitar using this finish. The first one I let it cure for 2 weeks before sanding and buffing the finish. I noticed that it sill seemed a little soft and wondered if I should have let it cure longer? It still buffed out really well but it did get harder in the weeks following.

Cheers,
Chad

Regarding cat nitro....it really does have that "burn in" like regular nitro?

Regarding cure time before buffing....I've used conversion varnish and like it, and the manufacturer says it can be buffed after 24 hrs. But it definitely buffs out better (i.e. is harder) after curing for a week.

_________________
The member formerly known as erikbojerik....

I used the MagnaLac in some situations where I was trying to get guitars out the door faster. It sands and buffs fine in 24 hours, but the shrinkage will kill you, as you have seen. I can't give you a "best" time to wait, though one guitar did end up getting re-sanded and re-buffed after 4 weeks and that held up a lot better than at one week. Depends on what your standards are also - a week of aging will look fine from a distance of 3 feet or more! As an ex-cabinetmaker, I am learning that some finishes take a lot longer to fully harden that I ever considered before. Lacquer at a year is pretty nice. In my one use of KTM9 it was still too soft at a year, but after 18 months it was a nice hard finish! Are you using Campbell's thinner? Cheapo thinners can really screw up the cure time.

I never had any problems with witness lines with MagnaLac, so I am assuming that there is some burn-in, but maybe I am just a good sander...not.

Off topic, but I am going to rant here - I wanted to switch to polyester and McFaddens minimum order was way too much for my meager output. I contacted the local ChemCraft dealer (160 miles away) and was pleasantly surprised how knowledgeable the finish guy was. I placed an order but after waiting several weeks for a direct shipment it never arrived. Called the store and found out they had fired the guy I dealt with because he had been there too long and they did not want to pay him what he was worth. - a cost cutting maneuver by head office. I was told that in those exact words. The new guy could not find my order and did not know anything about ChemCraft products. I gave up and called the ILVA company and had a great experience ordering cat polyurethane. Just finished my first guitar with that - still in the severe learning curve.

Brook

Thanks for the reply Brook.
In response to your question about thinner... I didn't use any... I was told by the employee who sold it to me that I wouldn't need to thin it to spray. It did seem to go on well, maybe I will experiment on some scrap with thinner just to see how it reacts for future knowledge.
Since I have some extra time before this guitar HAS to be completed I think I'll give it an extra week of cure time before buffing.

Cheers,
Chad