CA cure time

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tdibiasio

Member
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Aug 15, 2007
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Location
West Kingston, RI, USA.
I have recently embrased and have had good success with a CA finish, but have a question on cure time.

Here is my routine

Sand turned blank down to 12k MM with a DNA wipe between every grit
Grocery paper bag buff
3-4 coats of thin CA
Level with a light touch of 0000 steel whool
DNA wipe and buff the powder off with a cotton rag
3-4 coats of med CA (*** Forgot to mention this in the original post)
Here is were the question is......

Let sit overnight minimum to cure???

Is it necessary to wait over night to cure or can I start my final MM routine after an hour or so?


MM 3600 - 12k with DNA wipe between grits
plastic polish and buff off with lathe at 2700

I am converting from an enduro routine because it takes to long to finish, this new routine is much quicker, but I am trying to get it done even quicker if possible.

Any thoughts would be appreciated.
 
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Curing is something most people don't think about and most do not have a problem with. However, IF you want to prevent problems down the road when you move up to finer pen making - i.e pen that will be scrutinized by a few hard to please people with great eyes for detail, it is a good to take into account curing of CA.


I have finished a few pens with 3 - 5 coats of medium CA (equivalent to 8 - 10 coats of thin) in which the finish was perfect. Picts of it showed very smooth even gloss up and down the pen. Then later in the week, I saw minor ripples or indentations in a spot or two. The problem was part the wood and part the CA curing. The wood underneath had a knot and while it was smooth when finished, the knot telegraphed through within 24 to 36 hours and there was an irregularity on the finish. I took the pen apart and re-finished it and no more problems. What I just mentioned is not the norm but it does happen. This same thing happens with burls, with wood that has not been dried properly and with wood that moves a lot with humidity changes - especially cross cut wood grain. It is best to finish, let it set 24 hours and check again. Re-finish again if needed with another coat or 2 of CA.

I would like to make a suggestion on your work - 3 to 4 coats of thin CA are way too little IMO for a nice well done long term finish. Thin needs 5 to 6 as minimum. With thin coats and sanding - then sanding will take half of them off - depending on individual sanding style.

Another thing to watch for - DNA in some cases causes clouding. If it doesn't cause clouding in the CA with you, then no problem. However, if you do start getting a cloudy finish down the road, check the DNA usage.
 
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I let mine cure at least overnight because I noticed thet if I sanded and buffed immediately after finishing I was seeing micro scratches if examined closely. I started waiting overnight and they disappeared!I think it was russ fairfield who once posted that you needed at least an hour of cure time after finishing....somebody correct me if I'm wrong.
Lee I couldn't agree more. I've recently modified my CA finish. I used to begin with 3 to 4 coats of thin followed by 3 to 4 coats of medium. I started having issues with the finish lifting on the ends when I would dress them up before assembly. I got it in my head that the finish was too thick so changed to just thin. I started by using 4 coats. I quickly sanded through those 4 in places or noticed places like Lee mentions telegraphing through after a couple of days. So I increased to 6 coats....still sanded through in places. I finally settled on 10 coats of thin CA and lightend up the pressure when I sand. Result? a very consistant finish that is plenty thick and I don't sand through or lift the ends when cleaning up.
 
I have been having problems with the second coat of med. CA, it seems to wants to flake off (kinda) then I have to sand it down to the wood again. I thought it might be the BLO not drying, but I didn't apply it on the last one and it still did the same thing. Is there a brand of CA that is better than others?
My question is....how long should I wait before I start sanding? Do I put on the 3-4 coats of med. CA before I start sanding or should I sand between coats?

Thanks -
 
johnkofi said:
I have been having problems with the second coat of med. CA, it seems to wants to flake off (kinda) then I have to sand it down to the wood again. I thought it might be the BLO not drying, but I didn't apply it on the last one and it still did the same thing. Is there a brand of CA that is better than others?
My question is....how long should I wait before I start sanding? Do I put on the 3-4 coats of med. CA before I start sanding or should I sand between coats?

Thanks -
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John,

Much of CA finish is so "relative" in the application process. :redface: Simple statements are so often interpreted in varied range of meanings and perceptions. :eek:

Medium CA for me take about 3 to 5 minutes to set (sometimes longer) when I apply it with a rubber glove or some kind of applicator. One of my coats of medium is close to 3 to 5 of thin. IF I apply medium with _paper towel_, it only takes a minute at the most but the coating build up is like 2 thin coats - because so much of it is absorbed by the paper towel, but paper towel is a known mild accelerator of its own and the curing is faster.


Paper towel applications of med or thick can harden within 30 to 60 seconds. Other applicators, which put all of the CA onto the blank for a thicker build up - these take proportionately longer to harden - several minutes.



Back to your problem, the answer is relative. It would probably take 5 or 6 different stabs/ideas before the right one got nailed down. Hopefully one idea can help. I have never had a problem with "flaking or sorts" so that is not something I can speak to. I have had white spots. I get white rings when I sand at too high of a speed before the CA is properly cured. It will sand fine at slower speed, but high speed builds up heat fast and the sandpaper will grab a few pieces of dust, they will melt and it will create a white ring around the pen. I suspect that you probably need to let it cure a little longer.

Two things you can do that might help: 1. use accelerator; or 2. AFTER the CA is hard enough that it is not sticky, use piece of paper towel and lightly touch the CA'ed blank while it is turning at medium to slow speed. This will build up mild heat and accelerate the curing.
 
My opinion would be for you to not use anything but compressed air to clean the blank during the initial sanding process. DNA has too much water in it. Also, when sanding the CA use compressed air to get rid of the dust and then use accelerator to wipe down the blank in between coats. There's no water in the accelerator and wiping it down leaves just enough accelerator to speed up the curing time without any of the harmful effects that too much accelerator can have.
 
I will agree with the issue of burls and ca. I had to redo 3 burls yesterday I had finished 3 weeks ago.

But to throw another question in the ring. Does temp have much to do with drying time or clear/cloudy finishing? I've been having a bugger of a time the last few days since the temp has dropped.:confused:
 
Guys - thanks so much for the fast responses..... Hank - thanks for picking up on the fact that in my original post I only mentioned 3-4 coats of thin CA, I forgot to mention that after a light sanding with steel whool I add 3-4 more coats of med ca. ( I edited the original post to state this)

So I guess the general consensis is that waiting overnight is probably the best bet. Thanks also for raising the concern about using DNA, I have used it to wipe down blanks starting with the very first pen I ever made. That does not make it right, but I have not had any issues with clouding. I will now have a possible cause in my mind if I start to see issues with this in the future so thanks for that.

I guess I will stick to letting the blank cure over night, seems to be working fine, just wanted to know if others were waiting this long.

Tom
 
tim self said:
. . Does temp have much to do with drying time or clear/cloudy finishing? I've been having a bugger of a time the last few days since the temp has dropped.:confused:
Click to expand...

Temp does affect the drying and curing time. (I keep a hair dryer by my lathe in winter and use it from about a 8 to 10 inches away.) Humidity affects cloudy finishes more than temp. IF a blank hasn't been properly dried, then the internal moisture can be picked up as the finish cures and turn cloudy, IMO.
 
If you are seeing ripples develop several days after you finish the pen, they are the result of wood movement. This can happen frequently with burls, particularly dense burls such as amboyna and mallee.

I used to see the same ripples that others have mentioned here. Now I treat the dense burls the same way I treat pink ivory and snakewood. I turn and sand, then let them sit for a month or longer. Then I lightly sand again and apply a CA finish. This has prevented the ripples from forming. I use accelerator after each coat of CA. I apply, sand, and polish the finish in a very short period of time and there are no visible scratches, ripples, etc in the finish. It is not necessary to wait overnight.
 
Here's a stupid question for the group. I have been reading about the CA finishing process, but I haven't tried it yet. It's on my to-do list for this week. One thing that sounds a little strange to me is this: I've read that some woods are oily and therefore have to be prepared for the CA finish. But in some of the tutorials, we're advised to use BLO (i.e., oil) as an accelerant. So does oil prevent the CA from curing, or is it an accelerant?

I had to fix a large crack in a BOW blank last week and I used CA along with some of the turnings/sawdust from the blank. It worked like a charm, except that the area that was repaired has about a thousand times better shine than the rest of the pen.
 
leehljp said:
Temp does affect the drying and curing time. (I keep a hair dryer by my lathe in winter and use it from about a 8 to 10 inches away.) Humidity affects cloudy finishes more than temp. IF a blank hasn't been properly dried, then the internal moisture can be picked up as the finish cures and turn cloudy, IMO.
Click to expand...


Great(?) minds think alike, Hank. I have started using CA more of late and was considering a hair dryer for this time of year.
 
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