more CA problems!!!!

[amiers]

hi again, i am having big problems getting brass etch parts to stick.. the smaller parts seem to hold well but the larger bits, deck, hold but after a couple of days they lift or if you put pressure on some parts a section will pop up. i have tried painting them first and sanding both the plastic and brass. ideas please?

[Winks]

Are you isng the thick, gap filling CA or the thin CA? I use the gap filling, hit it with a little catalyst and have never had anything lift.

[Mike Glasgow]

I discovered that CA glue does get contaminated and does age, especially in damp hot conditions. I buy the smallest bottle of gap filling CA. I also place a drop on a piece of plastic and use it from there, being careful not to touch the bottle tip to the plastic. Try not to let the adhesive dribble down the bottle tip because it will distort the tip over time and prevent the cap from "snapping back on". I end up throwing away adhesive from time to time. You can store CA in the frigerator to prolong the shelf life. Hope this helps.

[amiers]

thanks guys, i am using both thick and thin. i have new bottles. it only seems to do it on larger parts. maybe its me!!!!!! i am going to scuff the brass etch a bit too see if i can get the glue to bit a bit more.

[kevinb120]

I use medium CA for just about all the assembly. Thin is really only good for model aircraft/balsa and thick is best for metal and glass. Thick takes way too long, and thin can wick inches away from what you are trying to glue precisely with one ill-placed drop. Medium has the best overall properties. It is thin enough to spread without clumping, stays tacky for a while before pressure is applied to the other part, and sets quickly when the part is placed. You can use activator or a mild heat source(tip of a cigarette somewhat close for about 2 seconds) if you are fitting a hard to hold part(like keeping a small antenna straight while it dries).

Occasionally I will use thin as a 'filler' for tiny cracks and then file it down, but never on painted parts. The CA most likely is old or simply the wrong viscocity. I have built countless RC aircraft and only recently got back into models(many of my scale aircraft used plastic for details though), but I prefer Bob Smith industries CA over every other brand for plastic, Zap would be my 2nd choice. Bob Smith products can be found with the hobby store "house label' sometimes but the bottles are colored blue for thin/purple for med/red for thick with a matching cap. Most stores that sell it usually have extra caps and nozles on hand too from the vendor. You use so little glue on ship models, having a few handy helps prolong the glue when the buildup gets too thick for the cap to seal.

Typically for small parts, I use a piece of 2" wide(x about 3") of masking tape on the table and toothpics and wires to apply the glue. Use a small drop on the tape and it is good for about 30 sec before it gums up. When the tape gets covered with 'dots' of dried glue, peel it off the table and stick another piece down. It will not eat through the tape. I never use the bottle to apply glue unless the part is very large-even superstructure joints are done with just a toothpic and a slightly larger 'dot' of glue. It takes VERY little to make something stick. Model RC planes eat glue up in vast quantities though(thats why they have such huge bottles), so only buy the small bottles for plastic kits, it will spoil long before you run out.

One other tip: the CA typically stays fresh when in something thick like a glue drop on one surface for much longer then when you press two parts together. As soon as it is compressed between two parts, it gets 'thin' and quickly burns off the acid(the stuff that burns your eyes, or 'smokes' with activator) and sets very quickly. If you have to re-set the part more then once, the glue is probably not going to hold well. I tend to avoid activator because it causes the glue to 'bubble' up way too much for tiny model parts. Inside a D-tube wing structure its ok(or MAYBE inside a hull joint where you would never see it), on finished models, its not. Activator can also cause paint problems, I would avoid it.

[TomD]

hi again, i am having big problems getting brass etch parts to stick.. the smaller parts seem to hold well but the larger bits, deck, hold but after a couple of days they lift or if you put pressure on some parts a section will pop up. i have tried painting them first and sanding both the plastic and brass. ideas please?

Sanity check: are the two surfaces to be glued completely clean? You won't get a good bond if they're not.

In my experience, CA-type glues are good for small, "fiddly" bits - anything that doesn't require strength. For large joins or parts requiring a strong bond, I use a two part epoxy, well-mixed. The drying time is slow but with it you get a comparatively long time to align the parts before the epoxy sets.