Epoxy Mixing Tips

General Discussion
1

 

OK, I’m playing this one straight. Many of you have better/different tips, and I hope you will chime in. I have watched a half dozen different laminators, good ones, and studied their techniques.  This is what works for me.

 

1.     Use a scale to measure the correct hardener/epoxy ratio.  45 to 100.  If I could attach EXCEL spread sheets I would put up my table used for the proper amounts.  Harbor Freight has scales for under $20.  Get one you can use for weighing your shortboards too.   A stoichiometrically correct mix (the right number of hardener molecules for hardener molecules) is the strongest.*

2.     If I miss the needed volume while pouring and end up with a few tenths of an ounce over for the resin, I use the 1:2 ratio for the added amounts for the hardener.

3.     I add the Additive F  last.  I have read here that some guys put the hardener in first and had a great reason for it.  I just can’t remember why.  NJsurfer, please chime in.

4.     For small amounts  (under 8 oz) the tongue depressor is a good mixing tool.  But cut off the round end, squaring it up so you can get in the creases of the cup or bucket.

5.     The amount of stirring will depend on the volume and the size of your stick.  Data point: for say 6 oz in a cup, I will stir for about 15 sec clockwise and 15 sec counter clockwise.  At the end of each 15 sec stir I scrape the inside of the cup with the stick 3 or 4 times and then scrape the stick back into the cup and tilt the cup so the liquid will flow over the scrapped liquid.  Do that 2 or 3 times.  For large volumes for say a LB deck, you will need to stir much more.  Use a big paint stir stick for that.

6.     For the bottom of the cup, I use the squared end of the stick and scrape the bottom corner of the cup and scrape the bottom in several directions.

7.     Lastly about 15 seconds of stirring and you are ready to use every single drop of resin in the cup and on the stick.

8.     After you pour it out, make sure you get the stick out of the cup so the remaining 1/16 of an inch of material will settle to a flat surface.  When you use the cup again, you will have a good surface to scrap against.

9.     It is much the same with a bucket and a paint stir stick.  Careful with those Home Depot sticks.  On a new one, the colored writing comes off in the epoxy and will leave some color in your mix.  Who knew? (Oops, that slipped out)

10.  Wipe off your mix sticks with scrap paper and reuse.  I like them seasoned with epoxy.  Seems cleaner.

11.  Store your cups and buckets up side down after the material hardens to keep trash out.  Don’t do anything to your cup or bucket that will compromise the clean smooth sides and flat bottom, otherwise it screws up your mixing next time. 

12.  Throw away your stir sticks and buckets if the edges are uneven with epoxy. Or the walls of the bucket have resin on the inside.  That will be an area you can’t easily scrape and mix.

13.  Don’t put anything except Add F in the mix.  If you do epoxy color, those buckets and sticks are one time throw aways. ( I know, it shouldn't matter, but it is cheap insurance)

 

*Most cups and buckets are conical in shape.  The volume depends on not just the depth but the varying diameter of the cup.  One inch of liquid in a cup is not half of 2 inches in the same type of cup.  Large buckets are harder to measure by sight because of the large surface area.  That is why labs us tall slender cylinders for accurate sight measurements of liquids and sight using the “meniscus” of the liquid. Look it up.  (Oops, another slip)

 

Let's hear from the rest of you.

 

2

hardener first so you have that coating the sides of the bucket and ensuring better mix.

if you do resin first, it clings to the sides and you have to then do a more thorough job of scraping and mixing to ensure you get some hardener molecules out there to the very edges to catalyze.

at least this is how it’s been presented relative to epoxy and resin-x mixing in previous posts.

3

Thanks Greg

4

I always use a paint brush to do the mixing, 20 plus years ago I had a RR hotcoat with ungelled streaks running throught it, I called Greg about what had happened, he wanted to know if I poured the contents out of the bucket onto the board, I said yes.

Greg told me it was unmixed resin or hardner from the sides or bottom of the bucket, ever since then I have been using a brush to thoroughly mix and wipe along the sides and bottom of the bucket, haven’t had any problems since then, I count to a hundred while mixing

5

1) Respect your elders.....

2) Scale or volume...get the ratio right...stir steady and smooth

3) If you live where it's cold....Move..... (or wait till summer)

4) Don't listen to Stingray.....

I glass all year long ,I don't use a scale, I never use a scale , I don't re-use mixing cups , I don't post cure , I use compressed air , I wash my hands  .....................................................................................................

6

stir for five minutes, scrapeing bottom and side regularly
do not reuse anything
measure 2/1 ratio

no problems

7

hi ,for small amounts of epoxy that is hard to weigh accurately i use food measureing spoons , they are small half round spoons on a set ,really cheap to buy but real easy to get the 2-1 ratio right ,i put in the harderner first just because it is thinner and it makes the resin not stick to the sides so much ,

i also freeze any left over resin that has been mixed with hardener rather trhan waste it , once taken out of the freezer it remelts and can be used for small jobs like sticking fins in place and filling dents etc, pete 

8

Use two buckets!

One for hardener, one for A. Pour hardener in A cup, stirr, then pour everything back in hardener cup and stirr.

This ensures a perfect mix. Even in the edges of the bucket.

9

    Howzit stingray, And it looks like you enjoy a few cold ones also, enjoy the ride. Aloha,Kokua

10

I think Benny had the great idea of using your extra resin to prep pre-preg strips of glass and resin and then freeze them for later use.  The idea would be to cut up some strips of glass, wet them out, roll them in wax paper or plastic and freeze them.

11

I follow the stingray method.  Volume measurements are easy, and they work.  Stingrays comments about temperate are also valid.  I have found that solids start forming in additive F when the temperature dips below 70 degrees.  I made a few mistakes relating to cold weather that I will relay here.

Mistake #1)  The temperature was about 62 degrees, and I noticed that there were solids in my Additive F.  I filtered the Additive F with a paper towel while pouring it into the resin mixure.  Don't do this!  I tried to apply it as a hotcoat over a lam that had been done with additive F.  It was fish-eye city.  Apparently, I filtered out the stuff that was needed to prevent fish-eyes.

Mistake #2)  For the next coat I warmed up my bottle in some warm water, and it became clear again.  I added it to the resin mixture and stired.  The problem is that I didn't heat up my resin, and the mixture went cloudy after I added the warm Aditive F.  I was applying it to wood, so any bit of cloudiness showed up. 

From now on I'm going to wait until the temperature goes above 70 degrees.

I used to add the resin first, but then changed do adding hardener first.  It is much easier to get an accurate volume reading when you add the hardener first, since it doesn't stick to the sides like the resin.  The minimum amount that I am able to mix in a cup is 3 oz.  I add 1 oz of hardener to on of those dixie cups with the volume markings.  I then add another 2 oz over resin on top of that.  I get the cups from a fiberglass supply shop that told me that they were ok for us with epoxy.  They gave me a whole bunch of bamboo stir sticks that have square edges.

12

I posted this on the test panel thread but this is probably a more appropriate place

Heated resin mixes much better than cool resins

counting to 100 is what I do also

 

I have yet to have a bad batch using this weight ratio. No calculator
needed

5g hardener to 11g epoxy

I made a table and posted
it on my shed wall

5:11=16 total grams of Epoxy/hardener

10:22=32

15:33=48

20:44=64

25:55=80

30:60=90

and
so on

anything less than 16 grams I just use 2:1 ration

 

cj

13

For Gloss coats i heat the resin up to 30 degrees Celsius,

It mixes nearly without bubbles

It spreads real nice

I don-t work in a cold environment though, heat the glassing room up to at least 20 degrees Celsius

mix by weight, pour hardener first, then multiply by 2,22 for the amount of resin

you ALWAYS have to mix Resin Research

14

For those of us who are barbaric Americans ,

20C is about 64F

30C is about 87F

Thanks Wouter

15

[quote="$1"]

I think Benny had the great idea of using your extra resin to prep pre-preg strips of glass and resin and then freeze them for later use.  The idea would be to cut up some strips of glass, wet them out, roll them in wax paper or plastic and freeze them.

[/quote]

I've been thinking about this pre-preg idea............

There's a power outage and a boatload of Swaylockers are running around trying to make something out of their Pre-preg before it thaws out and hardens......fun stuff....

 

Please don't re-use your mixing cups or use butter tubs or yogurt cups.....Step it up....have some pride.....you are building a Brand New Surfboard. Buy some good mixing cups........yes...buy some mixing cups. Stop being so damm cheap....How much did you pay for that QuickRipBong hat? Quality mixing cups cost next to nothing.......

(I'm poking fun at everyone...This is not an attack on Greg Tate)

 

Ray

16

1.  My office just ditched the scale we used to weigh stuff, and got another new digital scale from, of all places, the USPS.  The new scale is about 8 inches square by an inch tall, accurate to maybe half a gram, good to 5 kilograms (about 11 pounds) and will tare (measure the weight of the mixing cup, then zero the reading with the cup so you only get the weight of resin).  For, I'm told, about $20.  Unbeatable, I think.

2.  I have only used epoxy as an adhesive for little bitty projects (UV cure poly resin is soooo user friendly) but have a pal who works at a certain large hospital get me some disposable plastic syringes.  They come in useful sizes (1 cc, 5 cc, 10 cc, 100 cc, ...) but you should make sure they're unused or somehow "clean".  They can be re-used, just don't mix 'em up.

17

.