Learned something new about CA finishes Yesterday

[leehljp]

I have been using mostly CA finishes for about 7 1/2 years with 2 years off for a move from Japan back to the US.

After my first year of pen making and CA use, at some point in 2006, I started primarily using medium and occasionally thick CA. Of course, Medium and Thick takes longer to cure. I hate accelerators but on occasion use them when in a hurry. But they still cause as much problems as they fix. Accelerator tend to cause pits and make the finish more UNsmooth, and I don't like that. I have the normal and mild spray accelerator.

What I observed:
With my shop in the mid 80° temp range, I noticed that the first two coats of CA cured on one end before I could move a smooth coating to the other end (of a Sierra). Second coat, the same. (I was not using paper towel that absorbs 90% of the CA [wasteful, IMO] )

What I thought:
I suddenly had an epiphany: With the thin CA curing this fast, can I build up many thin coats faster - than I can apply 3 or 4 medium coats and their curing time?

What I tried:
I quit my pen making and got two blanks and my calipers, and not timing by seconds, tried a little experiment.

I had a .025 inch build up of CA (smooth, no ridges or dimples) between at 2 1/2 to 3 minutes. With Medium, It took me over 6 minutes for a .02 build up and hardening, including some minor ridges. Thin doesn't do this.
Caveat: I had a fan blowing over the work area, which probably affected the curing rate, but that was on both medium and thin. (In my thinking, the fan probably affected the curing rate of the thin [faster] than the medium.)

Again, this was not scientific but a personal observation on a single day. I do not use paper towel, but plastic/rubber gloves or plastic parts bags as the applicator-spreader.


Anyone else notice that a build up can be faster with thin than with medium? I am sure that temps and humidity may affect it also.

 

[glycerine]

Similar experience, the other night I was applying a CA finish. A while back, I had switched from paper towels to baggies and also started using medium and thick CA with accelerator. After applying the finish, I started to skew/sand it down. kept finding little pits and kept having to sand further, until, at parts of it, I had reached wood again. Decided to go back to the original way I applied my finished, which is just a thin CA with no accelerator and paper towels as the applicator. I found that I had a shorter wait time between coats and there weren't nearly as many bumps/ridges to sand back down!! The finish went on faster and came out smoother...

 

[EricJS]

Yes. I usually apply a couple coats of thin, then the rest with medium. Recently I ran out of medium and expected a timely application. To my surprise, I was finished in a very short time.

 

[jcm71]

Agree, Hank. When I first started using CA I used thin and could apply 10 coats (with BLO) inside of 5 minutes and it would be dry to the touch in no time. I have recently been experimenting with medium and the drying time is considerably longer, prompting me to use accelerator, which I never did using thin CA. Maybe it's time to go back to the thin stuff exclusively, as soon as I use all this medium CA I have. I was using paper towels but am now trying to perfect my "craft foam" technique (mixed results).

 

[danrs]

Thanks guys. Good info. Been using medium lately and wondering about drying time.

 

[jzerger]

I'm relatively new to the CA finish but used Medium with accelerator with no problems for dozens of pens. So, I bought some more Medium from a different supplier (Woodcraft I think) and it was "a lot" thicker than what i had before so had the bumps/sanding issues.
I started using some Thin I had recently and have the following show up once in a while:

There are white marks on the pen (after sanding and polishing) that looks like it's in the grain of the wood. Am I not putting on enough CA (usually only four or five coats)? I'm using a plastic finish (which is white in color) but will not buff out of the pen. This only happens on wood blanks.
I never had this issue before I switched glues.

Any suggestions ? Switch back to what worked seems too easy.
Thanks,
john

 

[Sylvanite]

Well, personally, I've had pretty good success building up CA finishes using med or thick CA with accelerator (from a pump bottle), as long as I don't try to put on so thick a coat that it foams.

One thing I have noticed, however, is that thin CA seems to accelerate medium and thick CA. If I have a coat of medium on, and I want it to harden faster, I sometimes put a coat or two of thin on top. The thin sets up at its normal rate and causes the underlying layer to harden. That technique can be helpful on cold, dry days.

I hope that helps,
Eric

 

[hanau]

I use medium ca then wet sand it I thought that looked great.
This weekend I tried medium ca with accelertator from woodcraft then buffed it out with tripoli and white diamond now it looks like glass.

I use what ever paper towels my wife has in the pantry no certain brand.

 

[leehljp]

I'm relatively new to the CA finish but used Medium with accelerator with no problems for dozens of pens. So, I bought some more Medium from a different supplier (Woodcraft I think) and it was "a lot" thicker than what i had before so had the bumps/sanding issues.
I started using some Thin I had recently and have the following show up once in a while:

There are white marks on the pen (after sanding and polishing) that looks like it's in the grain of the wood. Am I not putting on enough CA (usually only four or five coats)? I'm using a plastic finish (which is white in color) but will not buff out of the pen. This only happens on wood blanks.
I never had this issue before I switched glues.

Any suggestions ? Switch back to what worked seems too easy.
Thanks,
john

This is why there are so many ways to apply CA. One works for two or three people well but a different method works for a couple of other people and so on.

White below the surface or near the wood is usually a result of sanding and not cleaning, sanding too course of a grit and leaving scratches that accumulate CA sanding dust. CA sanding dust will look clear immediately when covered with wet CA but turn white when cured. Sometimes humidity plays a part in it too.


When I run into a problem, I don't just wonder what happened. Like the first post of this thread, when something unexpected happens, either good or bad, I stop what I am doing and investigate. Then I start experimenting to find if I can reproduce it, good or bad. If I can reproduce the bad, in this case, white streaks, then I know what is causing and will alter my procedure. If I find something good, I try to reproduce it until I can do it regularly.

Take time to enjoy the journey of pen making, which is filled with "discovery". The reason I say this is that there are probably several different reasons that cause the white spots. And it can depend on the technique used, or the humidity, or sandpaper grit, or pressure used in sanding, or cleaning method, layers, or temperature or other.

I alter my CA application depending on the temperature and sometimes with humidity changes. I learned this by just deciding that I wanted to know Why certain things happened. I did not learn all of it at once but with basic knowledge and repeatable shines, I later learned the way temperature changes and humidity changes affected CA applications later.

 

[robutacion]

Is great that people talk openly about these issues, allowing others to learn a lot and become aware of many factors that may have been ignored or simple unaware off, in this process of CA finishing/coating...!

One thing that I see mentioned all the time, is people using the term "thin", "medium" and "thick CA, an not making any reference to the actual viscosity of these various CA types. Where people run into troubles more often than not, is that CA thicknesses vary considerably from manufacturer to manufacturer and if this wasn't already enough, then we have the age of the CA, normally due to shelf time, either at the users location or at the purchasing place.

The time difference in between the CA manufacturing and actual using it, can be in many cases, years...! This alters considerably the CA integrity buy the way it performs. Lack of adhesion/strength is a factor but viscosity, is for pen makers, the most important factor. There also drying time differences and inability to self level, when then product (CA) is too old.

Looking at one of our excellent vendors (Monty, he was suppose to be the one to write this, I reckon...!), the manufacturer he represents, gives us a list of viscosities measured in "cups" and within the terms of thin, medium and thick, he also gives us various viscosities within the same thickness term such as thin CA from 5 to 50 cups, medium from 100 to 300 cups and thick from 700 to 1.500 cups.

Is obvious that, all these viscosities work slightly different when applied under the same sort of conditions so multiply that by the number of different condition people all over the world experience, particularly in temps and humidity levels and you have an enormous array of possibilities...!

It is true that, most manufacturers do not tell us the "cup" viscosity of the product, that alone is a culprit and reason to many troubles, as we don't have normally the manufacturing time stamped of the bottle.

So, when people mention think, medium or thick CA, that can mean lots of different viscosities in among each group so, is important that you have a reasonable idea of the true viscosity (in cups) of the product you are using...!

I know from experience that, since I start using Monty's CA's, I get not only a variety of viscosities that I have not seen anywhere else, particularly the very low cup's but also a clear labelling of what viscosity that CA is. I use all the time, 4 small 2oz bottles filled from the bigger CA bottles, the super thin (5cup), thin (50 cups), medium (300 cups) and thick (1.500 cups), each one has it own application merits and results something that was not possible when only one CA type in used, purchased from a place that has probably had it for years and nor an indication of is true viscosity, that my friends is cheap but, many times nasty and then reason of you CA finish failures...!

That's my .2 cents worth...!

Good luck

Cheers
George

 

[jzerger]

It seems my switching to Thin and still using accelerator was the problem. I made three pens yesterday with only thin CA and no accelerator (dries VERY quickly with the lathe on) with no issues (Bocote and Black Palm). I'm going to assume the use of accelerator caused the problem (white streaks...CA dust) until I have the problem again. I like the thin better as I put on very thin (no pun intended) coats to avoid ridge issues (less sanding). Admittedly, I only use a CA finish to preserve the wood color as well as make it shiny (only use 4 or 5 coats).
Thanks for all the help...the saga continues!

PS. As my "shop" is a part of my carport whatever the temperature and humidity is here is what my pens are subjected to...I don't charge extra for the sweat drops in the summer months.

 

[underdog]

So the moral of the story is...
To prevent streaks in your finish, keep everything clean, clean, clean.....
If you use dirty towels, or leave sanding grit or dust, or get wax/oil/metal in the finish, you're gonna have problems.

Interesting observation about the thin going on faster. I saw a youtube vid about a guy who puts on 20 coats of thin CA in just a few minutes and uses accelerator on every coat...

As for the manufacturers of CA, I'm sure as more and more turners use this stuff for finishing, more manufacturers will address the problems we have with it, and make it more predictable. Of course as unpredictable as it is now, perhaps it'll scare enough turners away that they won't?

I dunno. Just wish it weren't so tricky... There seems to be no real substitute for CA finish on pens.

 

[jzerger]

I should also mention that I don't have a VS lathe so it is either on or off and have the belt on the middle pully (Turncrafter 10"). It looks like most people set their lathe much slower speeds for CA finishing...you do have to be fast with applying the glue evenly.

 

[leehljp]

It seems my switching to Thin and still using accelerator was the problem. I made three pens yesterday with only thin CA and no accelerator (dries VERY quickly with the lathe on) with no issues (Bocote and Black Palm). I'm going to assume the use of accelerator caused the problem (white streaks...CA dust) until I have the problem again.

Don't totally give up on accelerator. When cooler weather comes, accelerator or BLO help speed up the curing process just a tad. The curing "assistance" of the two are not needed in very warm weather. As to the white streaks, that does happen but they can be avoided somewhat with practice and experience.

 

[jzerger]

Thanks for the advice and encouragement...I'll keep making things smaller and rounder. I hadn't really even considered the temperature impacts (other than complain when I'm not comfortable).
I keep learning and experimenting...love this site!

 

[arcwick08]

I'm voting for enviornment making one of the biggest differences in quality of CA finish. I'm up here in Vermont and depending on the season our temperatures and humidity levels swing wildly, sometimes day to day. While my basement is a bit more controlled, I have to completely change my application MO depending on the week.

In the cooler, dryer fall & winter, I use a couple THICK coats of THICK grade CA and get amazing results. Come the humid/wet spring and summer and that method no longer works. I have to switch to the ~12 thin coats method.

 

[jzerger]

Thanks again...as I just started using a CA finish about 6 months ago (when the Medium worked great) and now the Thin (lots of layers) works great it probably is the temperature/himidity rather than the accelerator (I used thin and accelerator yesterday and it worked fine). Thanks again, i usually blame myself for not doing something right.

 

[lorbay]

Yes Hank I can apply thin in way faster time than Med or Thick + I can get it thicker

Lin.

 

[flippedcracker]

I think I need to experiment more. I've been using a CA/BLO technique that's really worked for me, and haven't noticed it being slow. But I guess I also don't have anything to compare it to. And maybe the BLO helps it cure faster. I start with a couple of coats of medium, and then use thick for the rest.

 

[leehljp]

I think I need to experiment more. I've been using a CA/BLO technique that's really worked for me, and haven't noticed it being slow. But I guess I also don't have anything to compare it to. And maybe the BLO helps it cure faster. I start with a couple of coats of medium, and then use thick for the rest.

If you are applying with paper towel, the PT is absorbing much more than is going on. In this case, there will be thinner layers of medium and thick, which will cure faster. And you are correct, the BLO does act as a mild accelerator itself.

 

[BangleGuy]

Awesome thread! I am new to CA and am learning more all the time. I do think the viscosity is rated in Centipoise (CPS), but I read other literature that talks about a Zahn Cup. So I am not sure which units of measure is fitting for a 'cup'...

I would guess that thick being 1500 and med 300, then thick is 5 times more viscous than medium, and so on.