The Framers Forum

As a newbie and supporter of recycling I thought that Polcore was the way to go. However on using it I've not found it is not so easy. I find joining the mitres tricky with the underpinner, a spot of super glue in the wrong place and it doesn't wipe off the moulding surfaces and the plain finishes scratch and mark very easily. Would love to know anyone else's experiences and if there are any hints to make it easier otherwise I might remove them from my selection altogether.

is plastic not made from oil?

there is a lot of pefc mouldings about

When joining Polcore the wedges need to be positioned away from the back edge.

Superglue will not come off anything so you should only use a very small amount on one surface.

I can't see where you have purchased Polcore from us so I assume it was from one our distributors. If you would like to message me I can arrange a visit from our sales agent to help or I can phone and can talk you through it.

Ricky
Mainline Mouldings (Polcore)

I've been using Polcore mouldings for a while, and I almost gave up at first! I've learnt a few tips through trial and error that might be of use.

In my experience, superglue-type adhesives are a waste of time - they're too thin so you get very little surface-to-surface contact, and the working time is so short it's usually gone off by the time you get the joint in the pinner.

After asking for advice on here, Titebond Polyurethane glue was suggested, and whilst not perfect, it does work quite well and has the advantage of being wipeable-offable with a damp cloth.

I've also found it best to use much smaller wedges than you would if it was a timber moulding, and of course, follow the advice of not putting wedges further than halfway towards the outside edge.

I find smaller frames give me more agro than larger ones, and I more often than not use band clamps. These from Screwfix are so cheap, it's good to have a few for this purpose. I glued a bit of brushed nylon loop fabric into the corners just to protect the moulding but at 5 quid a pop, they do the job splendidly.

I'd much rather spend all day gluing/pinning a good quality timber moulding, but I'm now getting consistently good results with Polcore. Hope this helps!

http://www.screwfix.com/p/adjustable-band-clamp/16857

Why not just use PVA?

Poly moulding does vary. When it's made, an agent is added to the mix which gives off gas. This forms tiny cavities to create a sort of 'crunchie bar' effect which makes the plastic sligthly porus. So actually PVA will stick up to a point depending on the pore structure. To really stick it you would need polystyrene cement which has a strong solvent and virtually welds the joint together. But with this stuff any stray bits will strip the finish.

Why not just use PVA?

Poly moulding does vary. When it's made, an agent is added to the mix which gives off gas. This forms tiny cavities to create a sort of 'crunchie bar' effect which makes the plastic sligthly porus. So actually PVA will stick up to a point depending on the pore structure. To really stick it you would need polystyrene cement which has a strong solvent and virtually welds the joint together. But with this stuff any stray bits will strip the finish.

I've experimented with ordinary PVA, but even after a couple of days, the glue can remain wet. That Titebond stuff is quite weird - it behaves more like an epoxy. It seems to expand to fill joints (which is why clamping gets better results) and you have to be careful not to overglue the joints as it has a tendency to bubble out whilst curing. Having said that, any excess scrapes off quite easily with a fingernail.

I find PU MAX POLYURETHANE WOOD ADHESIVE, from Lion Mouldings excellent for polymer mouldings.Using a very small amount,as it expands, and keeping away from the edges.Clamp the frame up over night, then the next day underpin.Perfect...
pete...

By the way.Acetone, avaliable from the chemist, is the solvent for PU MAX...

Lighter fluid is pretty good too.

I stick polcore with Bison plastic glue. You still have to be careful not to use too much glue, because you can't get remove it from the surface of the moulding, but the glue produces a very strong mitre.

It is a solvent based glue and can slightly soften the core of the moulding, so the glue needs to set fully over night, which will also allow any softening of the moulding to become fully hardened again.

Thanks everyone for your comments I will take them all on board and keep practicing. I might well take up Ricky's offer too from Mainline Mouldings for a sales visit. Thanks Ricky.

is it worth all the effort of clamping overnight etc. do yo actually save anything?

We use tons of Polcore moulding on all sorts of jobs from 5x7 pictures of kids to football shirts and manage to join it using the mainline super glue and prefer to use a 10mm wedge where on wood a 12mm wedge would be better. As has been said keeping the wedges well away from the outer edges is a must to avoid spreading but we now rarely have this problem.
On occasions you will find that the depths aren't always identical so if possible make your frame from the same length.

I use a lot of the Polcore moulding and I too have problems joining them..... at times.
I can't glue them as I have to make up hundreds at a time, so from a price aspect it is not viable. I can only underpin them and hope !!!!
The main problem I get is that the bottom surface of the moulding is not always flat especially on the narrow ones I use and the pieces "roll" on the underpinner thus leaving an open gap on the visible top face of the frame.This of course is after having cut them on my Morso where I imagine they will "roll" a bit whilst cutting. Not an acceptable result no matter how cheap the frame is priced up at.
Unfortunately this varies between batches of the same moulding so a good tight frame today can be a loose looking load of rubbish in a few weeks time.
I imagine this is a manufacturing problem but how it comes about is beyond my remit.

Surely this is because of the lack of adhesive...


"Unfortunately this varies between batches of the same moulding so a good tight frame today can be a loose looking load of rubbish in a few weeks time."