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 Post subject: Odd shellac experience
PostPosted: Tue Sep 18, 2018 1:48 am 
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Cocobolo
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I usually have very good luck with Shellac. It is my go-to finish. A while back, I got a little lazy after filling with pumice and shellac and decided to build coats using spray can shellac (vs. FP). Roughly two years later it is still soft. It is not gummy, but if I lay it on a terri-cloth for more than 15 min the finish starts to get deep divots from the towel. I called the vendor and checked the lots and the shellac was not old. I keep it hanging in the shop and test it from time to time - still soft . I have gotten glass hard finishes frm shellac in the past, using FP method.
Any idea what is going on here? Thanks.

GS


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PostPosted: Tue Sep 18, 2018 4:42 am 
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Brazilian Rosewood
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Do not know the cause though water contamination is a likely suspect. I do know hat if it did not get hard in 30 days it will not do so ever.

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These users thanked the author B. Howard for the post: gxs (Tue Sep 18, 2018 2:56 pm)
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PostPosted: Tue Sep 18, 2018 10:10 am 
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gxs wrote:
I usually have very good luck with Shellac. It is my go-to finish. A while back, I got a little lazy after filling with pumice and shellac and decided to build coats using spray can shellac (vs. FP). Roughly two years later it is still soft. It is not gummy, but if I lay it on a terri-cloth for more than 15 min the finish starts to get deep divots from the towel. I called the vendor and checked the lots and the shellac was not old. I keep it hanging in the shop and test it from time to time - still soft . I have gotten glass hard finishes frm shellac in the past, using FP method.
Any idea what is going on here? Thanks.

GS


I don't have any experience with "real" shellac, but I got frustrated with a guitar body I was working on and decided to just finish it with some of that Zinsser dewaxed spray shellac I had kicking around. I ended up with the same thing, it never really cured, and took on the texture of anything it laid on.



These users thanked the author Conor_Searl for the post: gxs (Tue Sep 18, 2018 2:56 pm)
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PostPosted: Tue Sep 18, 2018 3:00 pm 
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Cocobolo
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Yep, that is what I used. I called them and they said that should not happen (except it did). I think I am going to stick with mixing my own, which has alwsys worked well for me.



Conor_Searl wrote:
gxs wrote:
I usually have very good luck with Shellac. It is my go-to finish. A while back, I got a little lazy after filling with pumice and shellac and decided to build coats using spray can shellac (vs. FP). Roughly two years later it is still soft. It is not gummy, but if I lay it on a terri-cloth for more than 15 min the finish starts to get deep divots from the towel. I called the vendor and checked the lots and the shellac was not old. I keep it hanging in the shop and test it from time to time - still soft . I have gotten glass hard finishes frm shellac in the past, using FP method.
Any idea what is going on here? Thanks.

GS


I don't have any experience with "real" shellac, but I got frustrated with a guitar body I was working on and decided to just finish it with some of that Zinsser dewaxed spray shellac I had kicking around. I ended up with the same thing, it never really cured, and took on the texture of anything it laid on.


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PostPosted: Tue Sep 18, 2018 3:06 pm 
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Cocobolo
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Brian, I imagine some day I'll pass away working in my shop (hopefully years from now), and someone will come in and wonder why there is a dusty guitar hanging there, and then notice the finish is still soft. Another note - the spray can stuff doesn't seem to blend/melt as well with my homebrew of shellac and Everclear. They must denature with something weird like bubblegum or something.


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PostPosted: Tue Sep 18, 2018 4:14 pm 
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Maybe there was a bad batch or it somehow got moisture in it?

I use the Zinsser Bulls Eye all the time to seal tops while I'm working and to prep rosette and binding channels. What I've got is probably 3 years old and I just sprayed a top with it a few days ago. It dries fine. My shop stays at 45% humidity so not likely to get water in the shellac. I always mix my own shellac for finishing though.

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PostPosted: Tue Sep 18, 2018 4:57 pm 
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I've had this happen to me twice. Once was a tabletop French Polished with orange shellac. The weight of a lace doily would leave an imprint in the finish.

The second was a vase finished with heavily dyed blonde shellac. Months after being finished, a business card left in the bowl would dent the finish. I eventually decided that I had sprayed the shellac on too thick (the layers were both too thick and applied too often - since this was sprayed onto a turned piece on the lathe, it was easy to apply heavy coats without sags). It could also have been due to bad flakes.

In both cases, the finish was freshly prepared shellac dissolved from flakes. The shellac dried quickly and wasn't sticky, it just never got hard. The advice I received is that this problem can happen if the flakes are old. With one batch the shellac flakes had been stored in my basement for a year before use. They dissolved readily enough, but the resulting finish never properly hardened. The other batch was freshly purchased super-blonde flakes - but they may have been old on the shelf or improperly stored during shipping. The flakes were partially stuck together in the container, but broke apart easily enough and readily dissolved. Nevertheless the finish was soft.

Based on my experiences I now apply shellac finishes very thinly and only use freshly purchased flakes. My guess is that the flakes you used were old or past their due date or had been improperly stored either by you or by one of your suppliers.



These users thanked the author Steven Odut for the post: gxs (Wed Sep 19, 2018 6:31 pm)
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PostPosted: Thu Sep 27, 2018 3:40 pm 
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Brazilian Rosewood
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I have used Zinsser on frames and other furniture type projects and have never experienced it. That is odd and obviously you are not alone. I would think that thick coats would simply take longer to dry or perhaps even craze but not remain soft forever. I wonder what age would do to the flakes to cause that too. I always assumed that as flakes they will last years but once mixed up should be used in about two months.


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