Christian.
Warping is a problem.
Gluing two pieces together is not such a problem as you can sandwich the two pieces between some flat ply sheets to dry.
When I painted some large xps panels I painted both sides at the same time and hung them on the washing line to dry luckily they dried ok and fairly un warped.
If coating a small panel on one side , in a thick coating of epoxy for instance , the panel will warp badly, I speak from experience, with a panel of mine !
I'm wondering if a thin scraping might fair netter ?
When I coated the 5mm xps in epoxy I think I waited until the wet side lost its tacky ness,but wasn't dry, and then turned it over and coated the other side.
When dry they seemed to even each other out, or maybe I was lucky ?
Steve.
Warping is a problem.
Gluing two pieces together is not such a problem as you can sandwich the two pieces between some flat ply sheets to dry.
When I painted some large xps panels I painted both sides at the same time and hung them on the washing line to dry luckily they dried ok and fairly un warped.
If coating a small panel on one side , in a thick coating of epoxy for instance , the panel will warp badly, I speak from experience, with a panel of mine !
I'm wondering if a thin scraping might fair netter ?
When I coated the 5mm xps in epoxy I think I waited until the wet side lost its tacky ness,but wasn't dry, and then turned it over and coated the other side.
When dry they seemed to even each other out, or maybe I was lucky ?
Steve.
Hi Christian/Steve
Firstly, Epoxy resins can shrink about 6% on curing so coating both sides in turn will probably help. If possible, don't let one side fully cure before coating the reverse side.
Using a thin type of epoxy will also help, or screeding it very thinly with a scraper
Shellac will also shrink but the coats are much thinner so the shrinkage effect is/should be less.
Also, I have found that if it occurs, warping can be corrected by 'backbending' against the warp using thin packers, clamping and applying another shellac coat or even just methylated spirits to reactivate the finish...leave clamped until dry..release and if the backbending rate was correct, the warp will be fixed
Coating both sides will help...Clamp down the very edges of the panel to a flat surface while coating. Leave clamped until dry, turn over and repeat on the other side.
Minimise rear coating to avoid weight gain
With practice, warping can be controlled.
PS..I found some great french polishing info on this site:
https://www.guitarsint.com/article/Introduction_How_To_French_Polish_Classical_Guitars
Cheers
Eucy
Firstly, Epoxy resins can shrink about 6% on curing so coating both sides in turn will probably help. If possible, don't let one side fully cure before coating the reverse side.
Using a thin type of epoxy will also help, or screeding it very thinly with a scraper
Shellac will also shrink but the coats are much thinner so the shrinkage effect is/should be less.
Also, I have found that if it occurs, warping can be corrected by 'backbending' against the warp using thin packers, clamping and applying another shellac coat or even just methylated spirits to reactivate the finish...leave clamped until dry..release and if the backbending rate was correct, the warp will be fixed
Coating both sides will help...Clamp down the very edges of the panel to a flat surface while coating. Leave clamped until dry, turn over and repeat on the other side.
Minimise rear coating to avoid weight gain
With practice, warping can be controlled.
PS..I found some great french polishing info on this site:
https://www.guitarsint.com/article/Introduction_How_To_French_Polish_Classical_Guitars
Cheers
Eucy
Eucy and Steve
Sorry I haven’t replied yet. You both raise interesting questions. But my daughter is getting married this weekend so I’m kind of busy. I’ll give you my full reply next week when the festivities are over.
Eric
+ @spedge
Hello Eucy, hello Steve
Thank you.
So no miracle, just learn to deal with warping what ever is the coating material!
I noticed in the last link you posted Eucy that cyanocrylate is listed as filling material with epoxy.
Christian
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For sure it is more important than DML. Enjoy the moment!
Christian
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Hi Christian/Steve
One lutherie website I found listed the different fillers they had tried and now they only use the scraped epoxy method
I'll try and find it again ...I'm on the road to Qld,. So only using my phone...not as convenient as my desktop
Cheers
Eucy
Grain filling again:
https://www.woodworkforums.com/f98/alternative-pore-filler-hard-shellac-113505
And a cautionary tale from Perth (Aus) on the dangers of epoxy
http://www.anzlf.com/viewtopic.php?t=1056
Eucy
https://www.woodworkforums.com/f98/alternative-pore-filler-hard-shellac-113505
And a cautionary tale from Perth (Aus) on the dangers of epoxy
http://www.anzlf.com/viewtopic.php?t=1056
Eucy
As usual after being away for a while, I turn on the system to see if it still sounds good.
Wondering if I'd been fooling myself as to how good the sound was ?
Once again I was pleased to hear very nice sounds.
I played this track off of a cd I'd never listened to all the way through (it's not really to my taste) so I was surprised to be very involved in the sound and the music .
The recording does not do the the sound in the room justice , but you can get an idea of the detail in her voice and the electronic echo fading into the background.
Just remembered I've got to send it to the computer and zip it 🙄
But in the meantime, this is a picture of the slight warp in this panel, not that bad considering it was 4 strips of badly warped crate ply glued together 😁
I'm not that bothered by slight warping.
And i have done nothing to this panel yet, so no coating ,no dust cone in the centre ,no weights , nothing!
Steve.
Wondering if I'd been fooling myself as to how good the sound was ?
Once again I was pleased to hear very nice sounds.
I played this track off of a cd I'd never listened to all the way through (it's not really to my taste) so I was surprised to be very involved in the sound and the music .
The recording does not do the the sound in the room justice , but you can get an idea of the detail in her voice and the electronic echo fading into the background.
Just remembered I've got to send it to the computer and zip it 🙄
But in the meantime, this is a picture of the slight warp in this panel, not that bad considering it was 4 strips of badly warped crate ply glued together 😁
I'm not that bothered by slight warping.
And i have done nothing to this panel yet, so no coating ,no dust cone in the centre ,no weights , nothing!
Steve.
Attachments
Hi Steve
I hope your well rested and tanned 🎣🪁following do a few chill out activities.
The recording has sounded very nice, keep on with the samples they are a thousand words for the uninitiated.
My few hours on with the TV and Glastonbury has me even more curious to have use of the DML's.
High Flying Birds Blew me away last night, and Robert Plant and Alison Krauss the previous night, and I missed Wolf Alice, anyways lots to look forward to.
I hope your well rested and tanned 🎣🪁following do a few chill out activities.
The recording has sounded very nice, keep on with the samples they are a thousand words for the uninitiated.
My few hours on with the TV and Glastonbury has me even more curious to have use of the DML's.
High Flying Birds Blew me away last night, and Robert Plant and Alison Krauss the previous night, and I missed Wolf Alice, anyways lots to look forward to.
The funny and seems serious recipe in this link is the grain filling with egg white... a post is even giving how to do with the remaining yolk... cooking! By the way, one white is enough for one guitar.
+ @spedge
"Would egg White stiffen a panel?" : who knows? It is said to raise the grain and to fill it. I have read nothing about stiffen effect.
2 questions :
"to raise the grain" : I know, and I found, no equivalence to that in French. To be sure about the wording : is it the first operation while applying varnish to have all the small piece of wood out of the surface, strong enough to be cut by sanding in order to get a smooth surface?
Guitar maker use Z-poxy as a filler. It is an epoxy to finish wood surface like stairs or floor. I search a bit around that and I found finishing epoxy product that seems fluid and cure very slowly (1h30). Their purpose is the protection of surfaces at home. Here is the only example I have found for now : resinence (sorry only in french). Main application seems to be with a roller. Does somebody have experience with? Is it a kind of product candidate for our kind of applications?
"Would egg White stiffen a panel?" : who knows? It is said to raise the grain and to fill it. I have read nothing about stiffen effect.
2 questions :
"to raise the grain" : I know, and I found, no equivalence to that in French. To be sure about the wording : is it the first operation while applying varnish to have all the small piece of wood out of the surface, strong enough to be cut by sanding in order to get a smooth surface?
Guitar maker use Z-poxy as a filler. It is an epoxy to finish wood surface like stairs or floor. I search a bit around that and I found finishing epoxy product that seems fluid and cure very slowly (1h30). Their purpose is the protection of surfaces at home. Here is the only example I have found for now : resinence (sorry only in french). Main application seems to be with a roller. Does somebody have experience with? Is it a kind of product candidate for our kind of applications?
Hi Christian
Q1...It is believed that the first grain rising is the greatest...so if you force it with a light water spray or similar, then sand it back after drying, the worst of the grain rising has been overcome
Q2...No experience with that brand..but a light coat of thin epoxy is what you're after...definitely not a roller application
I'd pour a small amount on and spread with a plastic scraper.
Cheers
Eucy