How thick is a coat of CA? :)

[edstreet]

I keep reading all these post where people claim x coats of CA. What I am curious about is how thick is 1 coat of CA? One post was 15 coats which if even thin they add up very quickly.

 

[joefyffe]

I'm anxious to see the answers to this one. It seems I can stand there half a day applying coat after coat after coat and maybe get 3 or 4 thou build up! It's a good thing I like Whiskey so I have something to do between coats. Another thing, I am reluctant to use kicker so allow most to time/air dry. Ohhhhhh! CA bores me sooooooo bad!

 

[jmbaker79]

Would say it depends on application method. For instance 10 coats of medium on craft foam,etc would be thicker than ten medium coats from a paper towel...I'm sure every ones measurement would be different..

 

[stonyloam]

Interesting question, so dug out the micrometer. Kept it pretty simple: Brass tube, marked so I could measure in same spot every time. Applied CA with paper towel then accelerator. Remember this is a measure of the DIAMETER, so the thickness of the coating would 1/2 of the increase.

Results thin CA:
Coats 1 na blew the measurement
2 +0.0006"
3 +0.0009"
4 +.00005"
Medium CA (over the thin)
1 +0.0012"
2 +0.0010"
3 +0.0008"

There you go, quick and dirty measurement for what it is worth:wink:.

 

[edstreet]

Ok that makes good sense. However, you also have to look at the drop, the diameter size and how much area that drop covers. Does it go from end to end of the tube? Does it go for say 1/4 inch?

I see numerous references to "I used 30 coats of CA", which implies there is a set coat thickness. I could also see that as being "I used 30 DROPS of CA". I can also see it as "I applied 30 left to right coats of CA". I also recognize this is more likely epeen factors.

 

[stonyloam]

Did it the way I do it. Spread it along the entire length of the tube , at reasonably high speed, ran the towel back and forth a couple of times to even it out (accelerator between every coat). That's it. There are probably as many ways to apply CA as there are people doing it. I personally use 3 -4 coats of thin, sand smooth (600 w/d, d) then 3-4 coats of medium CA sand then polish, so my coating is not very thick when I am done. Works for me, but am still evolving:wink:.

 

[mredburn]

Granted you can measure each coat, but unless each coat is applied exactly the same as the first, which would be difficult in a hand application process, your measurements would be meaningless between turners. There is no standard for thickness, applicator type, lathe speed. right or left handed, physical condition, (including sobriety) of the person applying the Ca, Brand of Ca, thickness of Ca, length of blank. Porosity of blank Material on the first coat. Over all experience level of turning inclucing total amount of Ca finishes applied.

Also some turners sand between coats reducing the thickness of the application as they put it on and take it back off. How high is up? How blue is the sky?

 

[Dave Turner]

Terry's results match closely with my experience. I use medium CA and wipe on a drop using a folded Scotts paper towel, spraying with accelerator immediately after each coat. Each coat add's about 0.001" to my diameter. I typically put on 12 coats. When I tried 4 or 5 coats, I would occasionally sand through the CA in spots. This doesn't happen with 10 to 12 coats.

When I experimented with foam padding as an applicator, I obtained much thicker coats, but also more variability in thickness over the blank requiring more sanding.

 

[leehljp]

First, I rarely use paper towel in warm to hot months, so mine and others will build up much thicker than what was posted above.

Also, somewhat contary to what is above, I have found that for me and the CA that I use, I can get a faster and thicker build up with thin - than with medium. I posted a note on this a couple of months ago and a few others said the same.

Medium and thick take a few more seconds to set up and in some cases may take 10s of seconds to set up enough (without paper towel application) to allow for a second coat. In those 10s of seconds for medium and thick, several thin coats will go on and cure by the time of one coat for the others.

I only sand "between coats" when I start to get ridges or irregular glossy patterns. (Of course I sand after the build up is finished.)

Bottom line - as others have said, there is no standard. Paper Towel applications will cause the majority of the CA to be absorbed by the PT. But foam applications will cause 90% to build on the blank, causing a much thicker coat.

I imagine that those that do 15 to 30 coats do so because the PT absorbs so much of it.

 

[Xander]

I apply with foam, using a pretty good size 'drop' (more like 3 or 4 ), spreading over entire blank, then a few passes to even out. I do not count coats. First 2 are thin, rest are medium or thick, whatever I have.
To start, I turn below finished size by about .005, but sometimes I go more (soft wood - sharp sandpaper -oops). Then I apply a few coats of CA and measure. Add more CA, measure. When I get just OVER finished size I stop and sand to final size and finish with 9 grades MicroMesh and Plastex polish.

I do not use accelerator, and rarely sand between coats.

 

[stonyloam]

Granted you can measure each coat, but unless each coat is applied exactly the same as the first, which would be difficult in a hand application process, your measurements would be meaningless between turners. There is no standard for thickness, applicator type, lathe speed. right or left handed, physical condition, (including sobriety) of the person applying the Ca, Brand of Ca, thickness of Ca, length of blank. Porosity of blank Material on the first coat. Over all experience level of turning inclucing total amount of Ca finishes applied.

Also some turners sand between coats reducing the thickness of the application as they put it on and take it back off. How high is up? How blue is the sky?

Granted all of that is true, but we are not making sub micron ISO9000 measurements here, just trying to get a feel for the thickness of a coat of CA:wink:. From what I am seeing IMHO it would be reasonable to expect something like the numbers that I got.

 

[edstreet]

Interesting and a very wide range of answers. What I do is drizzle the CA on top of the spinning blank and a paper towel underneath to spread it evenly and go right to left, left to right and make 1-2 passes in this manner before sanding. After sanding there is 1 more go. I can control how much comes out and how much it's spread which yields anywhere from a very thin layer to a very thick layer.

One pen I did this weekend the after thickness - before thickness was 0.018 after application I put a satin/matte finish on it. So from this how many coats? By what numbers posted that would equate to 40 layers, there abouts. But this to is incorrect.

Basically it would seem better to say "My CA is X inches thick"

 

[stonyloam]

That is similar to what I do. Remember the thickness of the layer is only 1/2 of the increase in diameter, so it looks like it would be reasonable to expect between 0.0005 and 0.003 inches depending of course on application technique and about a million other factors.

 

[its_virgil]

I have never measured the thickness and I don't think I will start now. The thickness of the CA glue buiildup seems to be of little importance to the quality of the finish...to me at least. I apply 3 or 4 coats, sand if needed. Add another coat or two if needed or if I sand through to the wood. Wet sand and buff. Seems to me that more coats than needed is overkill and I have never needed more than 4 or 5 coats. Buts, if 30 coats are needed so be it.

Maybe the number of coats of CA glue needed is related to how much sanding is done to the wood prior to starting the finish and not to how many coats are needed to get a good CA glue finish.

Do a good turn daily!
Don

 

[edstreet]

I have been watching a few other threads with interest and I think I may have a reason for the 15-30+ coats of CA. One thing that I have been noting is over use in the sanding/buffing/polishing department. These will all do the same thing: make your coating very thin very fast.

 

[leehljp]

One misleading perception on several of the posts: depth and number of layers should not be the final goal or purpose. Depth and or number of layers misses the point! Layer and depth build up should be to a measurement equal to the level of the nib, CB and clip end when finish sanded.

 

[edstreet]

One misleading perception on several of the posts: depth and number of layers should not be the final goal or purpose. Depth and or number of layers misses the point! Layer and depth build up should be to a measurement equal to the level of the nib, CB and clip end when finish sanded.

Well said, I did a quick search on the forums and found the following.

"coats of CA" in:
Pen Turning forum: 153 hits.
Finishing forum: 241 hits.
Casting & Stabilization forum: 21 hits.
Other things we make: 20 hits.
Show off your pens: 500 hits.
Tip tricks and FAQ: 3 hits.
Pen Photography: 1 hit.
Fountain Pens forum: 1 hits.
Advanced Pen Making forum: 11 hits.

Would appear that the search is limited to 500 entries so I broke them down to each forum and listed by thread so you can say "coats of CA" a million times in one thread and it only counts as one entry.


So my follow up question/concern is why are people using high coat numbers unless it's epeen factors?

 

[nativewooder]

Such a question is answered by so many different people with so many different aspects that you might as well ask, "how thick is (a layer of) sunshine?"

 

[RichB]

How much pressure you put on the application pad makes a big difference on the thickness. You can push the CA to the ends to build them up just by adding more pressure. So it is hard to figure out how thick one coat is. Everyone does it different.

 

[joefyffe]

Granted you can measure each coat, but unless each coat is applied exactly the same as the first, which would be difficult in a hand application process, your measurements would be meaningless between turners. There is no standard for thickness, applicator type, lathe speed. right or left handed, physical condition, (including sobriety) of the person applying the Ca, Brand of Ca, thickness of Ca, length of blank. Porosity of blank Material on the first coat. Over all experience level of turning inclucing total amount of Ca finishes applied.

Also some turners sand between coats reducing the thickness of the application as they put it on and take it back off. How high is up? How blue is the sky?

Mike: I caught that!! :biggrin::biggrin:

 

[Dave Turner]

I agree that CA thickness per coat is totally dependent on the application parameters. What is important is that people are aware of the total CA thickness and how it contributes to the final fit of the components.

As someone who turns between centers (mainly because I could never master using a mandrel), I am constantly measuring my blank diameter. I shoot for a final polished CA surface 1 or 2 thousandths of an inch proud of the component diameter. To achieve this, I need a rough idea of how thick my CA finish will be.

I find that most component pieces have a relatively sharp edge where they abut the blank. If the blank is even a tiny bit shy, you can feel this edge with your fingernail after pen assembly. I try to keep my blanks a few thousandths proud and I will microscopically bevel the edge of the CA with the last few grits of Micromesh. This permits a nice tactile feel to the component joint when you rub your finger in either direction. There's no perceptible "catch".

 

[Texatdurango]

Another opinion..........

I've often said in these discussions that the term "COAT" was totally meaningless when used in describing the thickness of CA being applied and a thread earlier this year proved my point.

The pen maker mentioned that he applied a few dozen coats and was complaining that when he started sanding that he was seeing dark and light areas and thought the CA was somehow bad. After some discussion, it turned out that he was sanding totally through the CA, back into the wood blank.

So much for "Two dozen coats"!

When I do CA finishes I decide the thickness I want beforehand and if the dimensions of the mating pen parts are .500", I would turn the blank to .495" for example then build up the thickness so that after sanding and polishing, the blank with the CA is the same diameter or slightly thicker than the mating parts. To me, it doesn't matter how many applications it takes, or whether you sand in-between applications it's the finished diameter that counts.

I have a sneaking suspicion that some have heard the terms used in other areas such as... "This 1968 GTO was lovingly restored and has a candy apple red finish with 6 coats of lacquer" or "This beautiful roll top desk is finished with 5 coats of hand rubbed varnish." and bring this descriptive verbiage over to their pen making as a sign of a deep, rich looking finish.

But that's just me, I could be wrong!