Official Luthiers Forum!

Adhering to shelf life specs is certainly the safest approach, but I think official manufacturer's shelf lives are generally very conservative for cover your assets reasons. The actual shelf life in practice can depend a lot on things like how a material is stored or how often a container is opened and the material exposed to air, etc. For me, if a material I'm familiar with is behaving as it did when it was new, I'm comfortable using it rather than trashing it.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Snowman, if u noticed in the video, the guy paid no attention to volumetric ratio. I do not either. I'm still surprised lacquer thinner works. Is there a difference between lacquer thinner and mineral spirits?

Not sure
Maybe it was just the thinner he had in hand?
Mineral spirits or alcohol best for this ?


Sent from my iPhone using Tapatalk

I always used DNA, never seen thinner used before

Some people thin epoxy with acetone, which can be a major constituent of - cheap - lacquer thinners. Lacquer thinners are a devils brew of toxic waste products. Benzene among others(not benzine) used to be a favorite component but I believe is now generally outlawed. Acetone flashes off quickly and is relatively cheap and innocuous as solvents go.
I've heard 10% is the maximum amount of alcohol that can be used to thin epoxy, although West System suggests any thinning is detrimental to the mix and suggests warming the surface that it is to be applied to as a better alternative. There are a lot of things I see on you tube I just shake my head about.

I've used West Systems epoxy structurally in aircraft construction. We read and follow instructions and cautions and expiry dates to the letter. After making a test mix and observing its behavior.

For guitars, someone's mentioned that they use epoxies past expiry dates so long as it still works as expected. Problem is, it worked as expected the last time it was used. No guarantee that this time it will, and there's no way to predict that without testing first.

And I've never seen mention of mineral spirits being used in any way with epoxies. I would leave that can on the shelf.

_________________
Peter Havriluk

I've always used DNA because its an effective cleanup solvent for epoxy. It also flashes off quickly. I've never seen it chemically alter the epoxy. Its a wash coat. Just there to even the color.

Actually, what I said was I use it if it behaves as expected, not works as expected. In the case of z-poxy, that means the components have the same color and consistency as when new, they mix the same, the mix applies to the guitar the same, it sets up in the same amount of time, and it sands the same. The nearly three-year-old z-poxy I used on the current guitar behaved the same as when it was new. If the finish on that guitar craps out this year, I'll be sure to post it here. I suppose there is some chance it will, but I doubt it. I used the same two bottles of z-poxy on a guitar when they were two years old (one year past the shelf life date) and the finish on that guitar is still as good as new eleven months later.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

So here is the process on this instrument.
I did a pore fill with 2 coats of ZPoxy. Following that I sanded down as close as I could get to wood with the intention of NOT sanding through. An the shiny spots were leveled and of course some sand through occurred.

I then did as the vid suggested and applied a highly diluted wash coat. Color match achieved

I think a light white pad scuffing sand and this will be ready for lacquer




Sent from my iPhone using Tapatalk

Snowman, I highly recommend using an adhesion promoter before u spray, especially if waterborn. Also, u need to insure a good surface roughness for mechanical bond. 220 grit good. Body should look good and dull before you spray. Then hit with adhesion promoter, then do ur finish, Did u use DNA or lacquer thinner?

I used acetone


Sent from my iPhone using Tapatalk

Is there an adhesion promoter you recommend ?


Sent from my iPhone using Tapatalk

Really don't think an adhesion promoter is necessary if you sand back to 220/240.
I've done adhesion tests with Enduro Var over epoxy and they came out 100% (Epoxy/endure var/cross hatch finish with a sharp blade/ try to rip the finish off with duct tape well rollered on - no delamination of finish at all)

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Snowman - The guitar is looking really good. What lacquer finish are you going to use?

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

It is em6000


Sent from my iPhone using Tapatalk

My apologies, some reason I though you were using Enduro-Var

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

There’s a great tutorial by jay Lichty about this process. I’ll review it before spraying


Sent from my iPhone using Tapatalk

Thought i mentioned earlier. Prestech 58x1/58x2. Scuff the wash coat, spray it on, and ur ready in 30 minutes to start finish coat. Its a great idea to start with this adhesion promoter before apply epoxy. Especially for oily woods. My process is Prestech, Epoxy, Prestech, Finish. U can also spray top wood too, helps if u are using water born and want to eliminate grain rise. But don't apply to top until u are ready for finish application. It would protect the top, but it might attract dirt. Better to protect top with plastic carpet film till u are ready (I discussed this recently)

Snowman, did you spray the finish?

I haven’t done the finish yet. This weekend may be the first chance I get .


Sent from my iPhone using Tapatalk

Good. Just wanted to warn you that surface prep over epoxy layer (no wood exposed) with waterborne finish can be unreliable. I do not have enough data to say if same is true with volatile finishes (nitro, eg). At the very least, scuff that epoxy with 220 to aid with mechanical bond. At best add an adhesion promoter (after scuff)