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Deft cure time?


Michael H
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Dry time depends on how thick the build up is and how it’s laid on. Use thickened Deft but apply it in layers until you reach desired thickness. Let each layer dry before applying the next. You should be able scrape light shavings with a single edged razor blade. Do some testing on scrap pieces until you understand it’s characteristics. 

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3 hours ago, Michael H said:

Hello, I have not used deft much for leveling repaired cracks, but I happen to come across some in storage. How much time would you all suggest for deft to cure for leveling thin cracks before filing/sanding down?

I'd give it about three-to-ten years after application, before relying on it not shrinking any more. Tried it numerous times, and never managed to become a fan.

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5 hours ago, David Burgess said:

I'd give it about three-to-ten years after application, before relying on it not shrinking any more. Tried it numerous times, and never managed to become a fan.

And David has just named its *good* side. . .that it might dry some day. :-)

It seems to expand and contract differently from varnish, it doesn't sand well (resists sanding so you end up sanding varnish instead), scrapes poorly,  the polish doesn't match natural varnish, sometimes your retouching doesn't stick and peels off later if there's too much deft. Have I left anything out? Other than that it's sort of OK.

I use my normal retouching varnish, thickened to the point where  it will go on in dots that stay where they're put without spreading out (I wish I'd discovered that 35 years ago!), then I carefully sand with fine paper wrapped around a short piece of violin soundpost, for spot accuracy.

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2 hours ago, Michael Darnton said:

And David has just named its *good* side. . .that it might dry some day. :-)

It seems to expand and contract differently from varnish, it doesn't sand well (resists sanding so you end up sanding varnish instead), scrapes poorly,  the polish doesn't match natural varnish, sometimes your retouching doesn't stick and peels off later if there's too much deft. Have I left anything out? Other than that it's sort of OK.

I use my normal retouching varnish, thickened to the point where  it will go on in dots that stay where they're put without spreading out (I wish I'd discovered that 35 years ago!), then I carefully sand with fine paper wrapped around a short piece of violin soundpost, for spot accuracy.

I also use the retouch varnish for filling but can't say I've ever seen any thing that wouldn't shrink over time.

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22 hours ago, Michael H said:

What do you prefer?

I use a varnish I make especially for fill.  It's a little harder and clearer (you van hardly see it on the pallet) than my retouch varnish (I've put the basic recipe on the board in the past.  I'm sure you can find it is you really want to). If required, a bit of aluminum hydroxide can be added (for body in larger fills and ease of leveling with a sharp scraper). It dries relatively quickly, it's stable, retouch likes it, and tends to be resistant to swelling when exposed to alcohol.

I do know a number of very good restorers that do use deft, but I honestly never got along with it... Then again, I know some restorers can't quite get their head around how to handle the stuff I use.  

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Deft was wonderful when i learned to use it, in the high desert. I know folks in New Mexico and Utah that use it with color added for touchup, even. It shrinks, then it stops. Anywhere humid, prepare for days of laying a bead in, then waiting 36 hours, and then doing in again. It's doable, but if you want to avoid all the real frustrations Jeff and others laid out, make sure its dry when you put it in, and you give multiple thin layers time to cure.

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1 hour ago, Jeffrey Holmes said:

If required, a bit of aluminum hydroxide can be added (for body in larger fills and ease of leveling with a sharp scraper)

I am all for anything which might improve the task of leveling fill.    How much aluminum hydroxide do you add per amount of fill varnish?

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53 minutes ago, Brad H said:

I am all for anything which might improve the task of leveling fill.    How much aluminum hydroxide do you add per amount of fill varnish?

"It depends"  

Some who use it add the stuff 'till the fill varnish appears pretty "milky".  That works well for leveling purposes and adds a good amount of "body", but while the additive dries relatively clear, I find that too high a % (like enough to make the varnish "milky") can effect the reflectivity/clarity of the fill once it's cured.

That said; On wider or deeper fills it often takes a bit more than on thinner ones... but I try to add as little as I can get way with and rely on timing (level as soon as the fill can take the scraper well; which will depend on how fast your fill varnish dries) to make up for less aluminum hydroxide in the mix.  For me, that could be overnight to a few days depending on the depth and time of year.  Trial and error testing is the best way to get the feel for it all.

 

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The advantage of adding a powdered mineral to the filler is that the mineral won't expand and contract as the solvent content varies, like solvent-dissolved resins will. So displacing some of the resin with an "inert" mineral results in a filler which shrinks less when it dries, and expands less when subsequent coats of retouching are applied.

An advantage of aluminum hydroxide over some other possible choices is that it dulls scrapers much less than some other substances,  like powdered glass or silicon dioxide.

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3 hours ago, Michael H said:

Can someone explain the the process of using powdered glass? I am completely unfamiliar.

Glass spheres (Scotchlite, etc) needs to be used below the leveled surface of the fill varnish... and requires some tinting. It's usually used for deeper voids. Same goes for glass powder.  The stuff will eat up a scraper's edge.  

In the right hands, this sort of fill can be excellent.  We've covered the process a few times at Oberlin. 

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12 hours ago, Jeffrey Holmes said:

Glass spheres (Scotchlite, etc) needs to be used below the leveled surface of the fill varnish... and requires some tinting. It's usually used for deeper voids. Same goes for glass powder.  The stuff will eat up a scraper's edge.  

In the right hands, this sort of fill can be excellent.  We've covered the process a few times at Oberlin. 

I cannot seem to find a source for Scotchlite, will this work:

https://stemcelltulsa.com/products/retroreflective-beads?variant=29563355201649&currency=USD&utm_campaign=gs-2019-05-13&utm_source=google&utm_medium=smart_campaign&gclid=EAIaIQobChMIkZ3-7LDq5wIVTNbACh33lwyuEAQYAiABEgJJyPD_BwE

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1 hour ago, Joey Naeger said:

Just some food for thought. Deft is a brushing lacquer. As such, it's solved with retardants to slow dry time. Wouldn't a spray lacquer with a faster evaporation rate work better?

Yes, if the primary goal is to have the finish become dry to the touch as quickly as possible.  Spray finishes will still need to incorporate drying retarders, it the wish is to have them flow and level.

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41 minutes ago, Jeffrey Holmes said:

As John said, Kremer.

If you have reason to go this route, I  highly suggest you get some one-on-one pointers from someone used to using it.

Will do! I have several destroyed tops to try any unknown method on. I would like to rely less and less on my luthier over time, and it seems like I throw in the towel pretty fast, especially when it comes to aesthetic repairs. He must also grow tired of my questions,  although he has not expressed. 

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4 hours ago, David Burgess said:

Yes, if the primary goal is to have the finish become dry to the touch as quickly as possible.  Spray finishes will still need to incorporate drying retarders, it the wish is to have them flow and level.

True, a spray lacquer could also include retardants. Do we agree a lacquer could exist that's solved with only fast drying solvents?

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