CA finish eveness

[ToxIk]

So far in, whenever I go for a CA finish, quite often I seem to run into one particular problem. Whenever I finsh with CA, the finish is always thinner around the edges. Then when I go to sand everything down, I endup sanding through the CA and have to re-apply around those areas.

I figure this is a normal problem, seeing as it's always hard to properly seal sharp edges and corners. I'm just wondering if other people seem to have the same problem, and what may be done to mitigate it?

As an idea, I figure next time, I'll try resting the scales in positions such that, when drying, gravity draws the excess to the edges so that more cures at such areas.

[vladsch]

I tend to round my scales and I have the opposite problem most of the time. The CA tends to run off to the edges and is much thicker there.

When I see that the edges have a thin coat I apply a few coats only on the edges to build them up.

I usually build up 10 to 20 coats of CA before starting to sand. Even with all the attempts at building up a thick, even coat I still sand through some times. I suspect that it is also due to uneven sanding. Because of the shape some areas get more sanding than others. Edges being thin get more pounds/sq. inch during sanding.

Be careful about having too much CA in one spot. It may cure soft and won't polish up. I had that a few times and lately started using a tiny bit of accelerator spray after every coat to help it cure solid.

I have not had a painless set of CA finished scales yet but I am hoping to perfect the technique eventually.

[urleebird]

Yesterday was the best day to find another something to do...

[ToxIk]

I agree about rounding out the edges, it sure helps alot. However, if I round out the edges, then I can't get that nice one-piece look to the wedge without gaps. I tried rounding out all the parts except the butt end where the wedge is, but I couldn't quite get it and it just seemed off. I suppose with great precision it can be done, but I'm not sure if I can pull that off without lots of time invested.

I as well usually go to at least 10 coats of CA, sanding to remove large surface variations every 3 or 4 coats. The one thing that always happens that I really hate is the geometry the CA cures too. Even with sanding (but not heavy sanding), the CA always cures such that there's little pits left in the surface, and getting rid of them requires selective sanding. That or adding another layer of CA to help fill in the pits a little.

vlad, if the day ever comes that you perfect a smooth, easy technique, I will pay you to find out how

Bill, I do have your CD and have read the CA part a few times. I can't say I follow it to a Tee, but all the basics I do. There sure is some great info in there that helped when I first read it. My complaint in the main post isn't a huge one though, it's easily fixible. I was just wondering if anyone had some tips to avoid the headache.
Also, I think the main difference between my process and you're guide is "To sand between coats, I use my Burr King." I have no such luxury, and have been going only with hand sanding.

[urleebird]

Yesterday was the best day to find another something to do...

[portal5]

Bill‘s quote “Once I get the 10 coats on (maybe an hour's time) then sand the waves out”

Bill I get waves when the first coat dries! Do you coat over the waves up to the 10 coats or remove the waves as they occur? My scales have had many coats but sanding the waves off always finds its way through to the wood.
Tony

[urleebird]

Yesterday was the best day to find another something to do...

[ToxIk]

Thanks for the tips bill, I'll definitely try some of the other techniques on scales in the future. Perhaps it's my curing method where things seem to gum up. So far I've never used accelerators or heat guns. I just let the stuff cure in plain air for a few hours until it's fully cured. The thing is, I can put on a coat of CA and have it look like smooth glass, but after it cures, there's always some little nibs and valleys that develop. Could never figure out why.

[FiReSTaRT]

I have a large one that I just used to burn the oxidized top layer off the trim on the Golf. I guess it will take some extra distance and experimentation for it to work properly without burning the scale to crisp lol.

[vladsch]

The wavyness and bumps in CA come from uneven application because areas where the CA is thicker (in liquid form) tend to set slower.

As the thinner CA starts to set, the surface tension tends to pull the still liquid CA together, creating a much more pronounced thickness difference than can be attributed simply to a thicker liquid layer. I had big bumps, 1/16" higher than the rest of the surface, form if the CA is applied too thick in the worst cases.

Unless there is a trapped air buble, I ignore the uneveness and keep applying more CA layers until I am confident that there is enough CA to not sand through.

Latest attemps at CA finish, I did not sand the scales even on first few sandings. I simply sanded off the worst of the waves after about 6 coats and then continued to apply more coats, sanding every 4 to 6 coats, about 15 to 18 coats total.

I also thickened my CA. I took the red "Hot Stuff" (less viscous than water) and added some yellow "Hot Stuff" (thick like maple syrop) in about a 3:1 ratio. The main reason for doing this was to slow down the setting time to give me more time to spread the CA. The added bonus is that I get faster build up with less run off to the underside of the scales but have to be more careful not to have air bubble inclusions.

One thing to keep in mind is that I need that many coats to completely cover the brass work. If you are applying CA to an even surface then 8-10 coats should be plenty for a thick finish.

Jason, I have almost given up on getting to a painless CA finish. I now treat the minor rework in the finish as part of the game. Rework: grinding out air buble inclusions, which you can only see when you sand the surface flat, meaning that the bubbles are way down in the layer; applying more coats to areas that are too thin or sand through or have pits or dents that are too deep to eliminate by sanding the surrounding area; dropping the freshly CA covered scales on the garage floor, liquid CA covered surface down , and having to practically sand off the CA to remove all the crap that embedded itself in the finish.