Steve Maskery
Established Member
Fair enough. I've never done anything that needs close to an hour.
vacuum press woes
- Thread starter dave323
- Start date
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interesting debate,
It turns out I ain't doing a lot right here. Now I find there is a problem with my plywood as well. Which I have bought 5 sheets of doh! I bought it from mid sussex timber it was graded B,BB so I took it that it should be find to making boxes with but I think it may be structural plywood. Its birch as seems ok quality there are a few small voids inside but not many. The problem is the glue is not penetrate, when I try the water drop test it can take 5 minuites + on the top rough sanded outside surfaces to sink in. I read that idealy it should do it under 20 seconds and not more than 40 seconds!
There is a wealth of free information on the link bellow its quite long winded though:
http://www.fpl.fs.fed.us/documnts/fplgt ... ter_10.pdf
So maybe if I use a glue that takes ages to dry I can get around this. I hope! Anyone else experience this before? In the link on page 10-4 it takes about chemical interference to bonding which can come about through over dying of the wood surface or extractives (whatever they are) coming to the surface or intentional alteration, I think that may be refering to spray protectives and the similar.
I have some viscose epoxy which I will test on it which takes a couple hours to dry which whould be perfect. Never realised there was so much to glueing wood together
It turns out I ain't doing a lot right here. Now I find there is a problem with my plywood as well. Which I have bought 5 sheets of doh! I bought it from mid sussex timber it was graded B,BB so I took it that it should be find to making boxes with but I think it may be structural plywood. Its birch as seems ok quality there are a few small voids inside but not many. The problem is the glue is not penetrate, when I try the water drop test it can take 5 minuites + on the top rough sanded outside surfaces to sink in. I read that idealy it should do it under 20 seconds and not more than 40 seconds!
There is a wealth of free information on the link bellow its quite long winded though:
http://www.fpl.fs.fed.us/documnts/fplgt ... ter_10.pdf
So maybe if I use a glue that takes ages to dry I can get around this. I hope! Anyone else experience this before? In the link on page 10-4 it takes about chemical interference to bonding which can come about through over dying of the wood surface or extractives (whatever they are) coming to the surface or intentional alteration, I think that may be refering to spray protectives and the similar.
I have some viscose epoxy which I will test on it which takes a couple hours to dry which whould be perfect. Never realised there was so much to glueing wood together
RogerS
Established Member
dave323":h3d785sy said:
Just look at it....if it sucks down nicely then it's working just fine. Are your laminates straight or round a curved former, out of curiosity?
I'd also leave the stuff in the back for a good three hours.
Mostly it looks to have closed but on some sides of some pieces it looks less sucessful so I am still a little unsure and not content with the glue line all over. I think it could be possibly minor flatness problems perhaps. Like if you sand a piece the edges are real easy to round and make not flat which could result in a problem as even the vacuum cannot bring any bent together, but as I said still quite new to it so have not had enough experience to be expert in know exactly whats required and every pitfall.
Flat pieces, very narrow bonding area 12mm wide strips added to the plywood to add additional thickness for joints.
Mr T
Established Member
Hi Dave
One small point which I don't think has been mentioned. Do you put a piece of breather fabric inside the bag around the extracting outlet? This should extend from the outlet to the former. If you don't use this the outlet can sick to the bag and not provide full pressure around the former. I'm not sure what shape you are forming but you could laminate in stages if it's taking a long time to get the stuff in the bag.
I get my Cascamite from http://www.rydenor.co.uk/contact.html. Getting the mix right is important http://www.christribe.co.uk/blog/how-to-mix-glue/00074.html
Chris
One small point which I don't think has been mentioned. Do you put a piece of breather fabric inside the bag around the extracting outlet? This should extend from the outlet to the former. If you don't use this the outlet can sick to the bag and not provide full pressure around the former. I'm not sure what shape you are forming but you could laminate in stages if it's taking a long time to get the stuff in the bag.
I get my Cascamite from http://www.rydenor.co.uk/contact.html. Getting the mix right is important http://www.christribe.co.uk/blog/how-to-mix-glue/00074.html
Chris
