Sanding epoxy

[ccx2]

SO, ive used west system epoxy fillets with fast hardner, its been 15hrs and its rock hard. I want to sand it now, ill wear a resperator, longsleved shirt, gloves, googles, outside on a windy day, am i asking for trouble from sensitation?

[Lewisboats]

see other thread

[StevenBauer]

Who's downwind?

I don't sand epoxy anymore. Just use a heatgun and a sharp scraper. Works for me. No dust, much faster.


Steven

[Eric Hvalsoe]

A one time shot, with protection - I don't think you are in much danger of sensitivisation (sic). Relatively few people react immediately or harshly to epoxy. A reaction is usually triggered by repeated skin contact, or driving the stuff into your bloodstream by mistakingly 'wiping it off' skin with solvent. Of course everybody is different. Your epoxy may be rock hard but after only 15 hrs it is not fully cured, it is still 'green'. You don't want to breath the stuff. And as someone else alluded to, you don't want your neighbors to breath it.

[JimD]

I have actually never heard of sensitivity to cured epoxy but like Eric says, at 15 hours it's not fully cured. I'd wait another day, dawn a decent dust mask, and sand away. It'll sand better if you wait, too. Wash any amine blush off it first. I've been covered head to toe with epoxy dust and as long as I keep it out of my lungs there's no problem. Wet epoxy freshly mixed is where the sensitivity comes from, for me, at least.

[ccx2]

Ok thanks guys , in the mornin it will be .

[DuncanvdH]

What I am interested in is if barrier cream would also protect you(re face) from the dust. Or is barrier cream not something you should use on your face?

[ccx2]

I was going to put it on my face and hands to sand , but i think it intended for protection from wet epoxy.

[RodB]

Between sanding green epoxy and harsh warnings... these newbys are scared to death. How about lets be a bit more realistic... if epoxy is sandable (not gumming up the paper), the likelihood that they will be adversely affected is quite low. A simple dust mask ... will be fine... especially if you add in a bit of wind blowing lots of the dust away. As mentioned above.. I can't remember all the times I have been covered with dust from sanding epoxy glassed and unglassed panels...and fillets.... especially when its hot and I'm sweaty... dust just sticks all over you. Believe me the epoxy I am sanding is plenty cured enough at this stage. Also, I too use a good sharp paint scraper to decrease the amount of sanding needed, which is significant if you scrape at the right time.
The sanding of green epoxy complicates the equation for safety and is not necessary IMHO. Of course my personal experience is in a very warm climate and overnight is usually plenty of time to make for easily sanded epoxy that is very hard.


R

[SMARTINSEN]

I would second the sharp scraper recommendation. You can get almost all of the ridges, and the shavings just fall to the floor where you do not have to worry about breathing them. I follow up with a only just a very light and quick sanding, wearing a N95 mask, the making of dust appreciably diminished.

[spirit]

Remember that wet epoxy binds chemically to uncured epoxy, but that wet epoxy binds only mechanically to very hard epoxy; the latter bond requires that the hard epoxy is roughed up by sanding.

[Bill Huson]

Steven had it right - scraper. I don't use a heat gun, but I do knock down epoxy with a scraper. Stanley, nothing fancy. That and a small mill file. Scrape a few minutes, give scraper a few file licks, scrape some more. Cuts the lumps and ripples off epoxy fast! Scraper doesn't care of the epoxy is "green" or totally done. You can "shape" the scraper edge to suit. I have a small one I filed convex to scraper wookies off the inside surface of a canoe. Try it. You will learn to love your scraper :D

[ccx2]

Remember that wet epoxy binds chemically to uncured epoxy, but that wet epoxy binds only mechanically to very hard epoxy; the latter bond requires that the hard epoxy is roughed up by sanding.
Reading the West Systems instructions say that for a chemical bond recoat the previous coat should still have some tack to it, about like masking tape, if no tack when touched you are supposed to wait for it to cure and wash/sand for a secondary coat application. But from what i gather off this board alot of folks will recoat after it has set dry to the touch with no adverse affects. This being my first build im going with manufactures recommendation. Do you have good results otherwise?

[AstoriaDave]

ccx2,

There are too many variable to this. Some resins readily form a waxy residue called amine blush, and should only be recoated while tacky, or (if "hard) after a thorough soap and water cleaning and subsequent sanding. Others to not for amine blush and do not need the soap and water treatment.

What works for one formulation might not work for another. To assure a good bond, follow the manufacturer's instructions.

[RodB]

Reading the West Systems instructions say that for a chemical bond recoat the previous coat should still have some tack to it, about like masking tape, if no tack when touched you are supposed to wait for it to cure and wash/sand for a secondary coat application. But from what i gather off this board alot of folks will recoat after it has set dry to the touch with no adverse affects. This being my first build im going with manufactures recommendation. Do you have good results otherwise?

I 'm pretty sure we talked about this in one of your earlier threads... most folks try to do all epoxy work in one session so that you end up with more or less all epoxy chemically bonded as if done at the same time. If that is not possible.... then you have to be sure there is no amine blush, the surface is clean... and that the cured surface is "keyed" (roughed up for good adherence).

For example, I would not even begin a structural epoxy task (such as glassing or bonding joints) that I could not finish the same day. I think you get the idea.

RodB

[floatingkiwi]

I have a big portable fan. Positioned correctly I can paint, stick, sand, brush, roll, drill, grind, squirt, shake, mix, add, dissolve, wet out, spray, poke, parry and yahoo anything I want with zero respiratory aids and breathe and/or smell zero of it.

[gimmellsmom]

What I am interested in is if barrier cream would also protect you(re face) from the dust. Or is barrier cream not something you should use on your face?

Not sure what type of barrier cream in particular you're using, but in my experience with serious skin issues, most are petroleum based (i.e. mostly/90+%) which is basically vaseline and that's safe to use anywhere.

[Ray Frechette Jr]

A hand plane takes off epoxy goobers admirably. Far quicker and easier than a scraper.

Yeah, it dulls the blade and you have to resaharpen it and jeay you will wear away the blade with sharpening it and have to replace it someday. That is about the only criticiism about it that maeks any sense.

Replacing sandpaper and scraper blades is no more economy.

[DuncanvdH]

Not sure what type of barrier cream in particular you're using, but in my experience with serious skin issues, most are petroleum based (i.e. mostly/90+%) which is basically vaseline and that's safe to use anywhere.

It is ARRETIL from STOCKHAUSEN it specifically intended for protection against epoxy and polyester resin.

I do not want to scare anyone with the sanding issues, but the fact that our tutor at WoodenBoatSchool was so detemined about it made me think (again).

[JimD]

...im going with manufactures recommendation...

A wise decision.

[Boatsmith]

I've been working with epoxy for 30 some years now. I've been pretty good about keeping it off my skin. I had one kid who worked for me for a short time and was VERY sensitive to not just epoxy but green paint as well. The first trip to the emergency room didn't really make sense but the light went on a week later at the 2nd trip. He had to find another line of work.Other than that the only issues in my shop happened last year when we were building a 30' Wharram cat. This is basically a stitch and glue boat. We are in South FL and we routinely use fast hardener.so we can move to the next step quickly. WE had 8 men working on both hulls at once and were using halogen lamps to speed the process up. We were sanding a lot of green epoxy fillets and there was epoxy dust everywhere. We use dust masks and vacuum sanders where possible and also fans as sop. But with this many people in a small area and the quantity of green dust we started to see some problems. Just slight rashes on fingers and forearms, but enough to cause a reevaluation of our methodology. We now try and time our work processes to allow more curing time. We also arrange things to provide better separation from green dust,IE moving parts down wind to sand and vacuum dust up much more frequently. We haven't had any issues since. We are now more aware of the green dust problem and deal with it more appropriately.We also will fillet and tape and add fairing bog one after another to minimize in between applications. Sanding isn't only not good for you it's not very profitable which is two reasons to minimize it. David www.boatsmithfl.com

[ccx2]

I've been working with epoxy for 30 some years now. I've been pretty good about keeping it off my skin. I had one kid who worked for me for a short time and was VERY sensitive to not just epoxy but green paint as well. The first trip to the emergency room didn't really make sense but the light went on a week later at the 2nd trip. He had to find another line of work.Other than that the only issues in my shop happened last year when we were building a 30' Wharram cat. This is basically a stitch and glue boat. We are in South FL and we routinely use fast hardener.so we can move to the next step quickly. WE had 8 men working on both hulls at once and were using halogen lamps to speed the process up. We were sanding a lot of green epoxy fillets and there was epoxy dust everywhere. We use dust masks and vacuum sanders where possible and also fans as sop. But with this many people in a small area and the quantity of green dust we started to see some problems. Just slight rashes on fingers and forearms, but enough to cause a reevaluation of our methodology. We now try and time our work processes to allow more curing time. We also arrange things to provide better separation from green dust,IE moving parts down wind to sand and vacuum dust up much more frequently. We haven't had any issues since. We are now more aware of the green dust problem and deal with it more appropriately.We also will fillet and tape and add fairing bog one after another to minimize in between applications. Sanding isn't only not good for you it's not very profitable which is two reasons to minimize it. David www.boatsmithfl.com (http://www.boatsmithfl.com)
Very informative, thanks for posting.

[Candyfloss]

Why sand epoxy fillets? Laminate over them green or peel ply them.

[ccx2]

Why sand epoxy fillets? Laminate over them green or peel ply them.
Ive only one large 16' fillet under my belt but green and still tacky are two different states of cure according to West Systems directions and to laminate over green thats not still tacky would be a secondary bond that must be washed and sanded before another coat. If its still tacky then that would be a chemical bond and it can chemical mix i guess is the theory.

[RodB]

CCX2

The following is a general synopsis of the techniques for epoxy work bonding.

A) Fillet bond a joint, let cure... (hours, days or weeks) clean off any possible blush, sand with 60-80 grit... and apply biaxial cloth to the joint. Clean, sand and fair the biaxial to finish the joint. Some folks use peel ply to shorten this process.

---------------------------------------------------------------------

or...

B)Fillet bond a joint, begin to apply biaxial as soon as possible... ie., as soon as the fillet has begun to firm up some ... smooth over the surface of the biaxial with a chip brush and epoxy... not waiting, joint bonded in one session. Peel ply is used by some to minimize sanding of the finished biaxial.

This is a good example of how one can cut corners to achieve the same results in less time as your techniques improve in speed and quality.

Furthermore, if you are applying epoxy within a few hours of initial application, unless the temp is dropping alot, you are not likely to have any problems maintaining a chemical bond with just applying epoxy coats with no prep of any kind. I have been advised by a professional builder of more than 60 boats that usually even overnight in moderate temps... usually does not require any prep to continue applying epoxy. I believe the time interval mentioned was less than 12 hours. It is pretty easy to run your finger along the surface to see if any "waxy" substance exists. Its all about common sense.

Using System III, I can't remember ever having to prep epoxy surfaces for additional applications, because I have pretty much been able to do most jobs in one setting. If for some reason (once in a while) I had to wait between coats (say overnight or say 7- 12 hours).... I usually wipe the surface down with a 10% ammonia solution, then clean water... then slightly scuff the surface (remove shiny) with scotchbright, then proceed with epoxy application. I would say that I have still had a chemical bond from all appearances... cause when you cut thru such an application, you can see the visible effects of the secondary bond. In warm weather I would cut this time a bit.

If everyone here building epoxy composite boats followed every set of directions to the letter, many many boats would never get built. Remember, general instructions are on the conservative side... to insure the majority of folks have no problems.

RodB

[ccx2]

CCX2

The following is a general synopsis of the techniques for epoxy work bonding.

A) Fillet bond a joint, let cure... (hours, days or weeks) clean off any possible blush, sand with 60-80 grit... and apply biaxial cloth to the joint. Clean, sand and fair the biaxial to finish the joint. Some folks use peel ply to shorten this process.

---------------------------------------------------------------------

or...

B)Fillet bond a joint, begin to apply biaxial as soon as possible... ie., as soon as the fillet has begun to firm up some ... smooth over the surface of the biaxial with a chip brush and epoxy... not waiting, joint bonded in one session. Peel ply is used by some to minimize sanding of the finished biaxial.

This is a good example of how one can cut corners to achieve the same results in less time as your techniques improve in speed and quality.

Furthermore, if you are applying epoxy within a few hours of initial application, unless the temp is dropping alot, you are not likely to have any problems maintaining a chemical bond with just applying epoxy coats with no prep of any kind. I have been advised by a professional builder of more than 60 boats that usually even overnight in moderate temps... usually does not require any prep to continue applying epoxy. I believe the time interval mentioned was less than 12 hours. It is pretty easy to run your finger along the surface to see if any "waxy" substance exists. Its all about common sense.

Using System III, I can't remember ever having to prep epoxy surfaces for additional applications, because I have pretty much been able to do most jobs in one setting. If for some reason (once in a while) I had to wait between coats (say overnight or say 7- 12 hours).... I usually wipe the surface down with a 10% ammonia solution, then clean water... then slightly scuff the surface (remove shiny) with scotchbright, then proceed with epoxy application. I would say that I have still had a chemical bond from all appearances... cause when you cut thru such an application, you can see the visible effects of the secondary bond. In warm weather I would cut this time a bit.

If everyone here building epoxy composite boats followed every set of directions to the letter, many many boats would never get built. Remember, general instructions are on the conservative side... to insure the majority of folks have no problems.

RodB
Ok Thanks Rob, that clears things up, i assumed that since West is so adamant about it being tacky or somewhat liquid it has to be that way to mix itself for a chemical bond. Ive been very cautious because i didnt want any of my bonds to fail when the boat is in use:). Thanks for putting me at ease in future use.

[Mick Herron]

I use a heat gun and scraper occationally, although I believe the heated epoxy is a potential source of sensitizing vapors. I suggest caution with this technique as well.