RAAY!!! Why have you waited so long to share the secret of the PPG cup!?!??? Ha!
I mix by volume, and measure in the same old graduated 4 oz cups from TapPlastic over and over (Yes, I know, I do claim to be a “cheap ass master.”), and I’ve never had a problem. But, as Ray pointed out, I always wait, and am never in a hurry anyway.
Lots of things can come into play to screw things up. Did you zero the scale? Is it working right? Is it precise enough? If so, it will be the more accurate method. Volumetric is pretty fool proof. Fill it to the right line and you've got it. But! You might be on a slant, you might be tricked by the miniscus, you might be trying to measure too little for the cylinder which increases your error.
Oh the little things that are so easy to miss! Like Ryan says, all of these can make your mix incorrect which is why just filling to a line or even using scales can be asking for trouble without checking “the little things”. Also you say you used 12oz of RR but measured in grams. Are you sure you got the ratio from oz to grams correct? Double check you calculations as well. This has caught me out once before. And are you using a calculator? Don’t forget, the smaller the amount of epoxy, the more accurate you need to be with your mix.
6 boards ago was at least 3-4 bottles ago. Some boards have had problems while others have been fine. I’m not really sure why but I tend to use the same procedure for everything so I’ve been trying to eliminate error with each new board.
For the batch that was 12 oz I just happened to use a marked mixing cup. I poured in 8 oz of epoxy, unheated, and then figured out how many grams of hardener I would need. Then I microwaved the resin for about 10-15 seconds because it makes it so much easier to brush out. When I poured in the hardener I was watching the scale instead of the line markings on the cup. It was exactly 12oz after I had poured in the right amount of hardener.
I always tare the scale and I use a calculator to do the math.
I baked the board in the car for a good 8 hours yesterday, the temp was probably at least 85, I didn’t bother to put in a thermometer. I sanded this morning and the deck sanded very well. The bottom had some issues and I feel like the epoxy still isn’t as hard as I would like it to be. The finish had a very weird pattern on it, I can’t really describe it. Perhaps my Add F is faulty? I’ve always hated using the stuff anyway.
Not sure if I understand exactly what you did - if you measured the resin by the cup markings and then weighed the hardener on a scale, it may explain an off ratio batch although the final weight (12 oz) would roughly indicate that you did it correctly. With a small batch like 12 oz, a few grams here or there might be the factor that is giving you grief.
Some calibrated measuring cups are off. Suggestion might be to zero the scale, add resin then hardener so you are weighing both components. As has been pointed out, the gram or fractional gram scales give the best accuracy.
The weird pattern might be the additive. It also might be caused by different temperatures of the components after microwaving. The main thing is to stir the heck out it… several minutes is recommended. That would be several minutes after all components have been added. If the resin was really jazzed from the microwave, it might do weird things.
Do you recall how much additive you used and how it was proportioned - I.E. as a percentage of the resin, hardener or both?
Not sure if I understand exactly what you did - if you measured the resin by the cup markings and then weighed the hardener on a scale, it may explain an off ratio batch although the final weight (12 oz) would roughly indicate that you did it correctly. With a small batch like 12 oz, a few grams here or there might be the factor that is giving you grief.
Some calibrated measuring cups are off. Suggestion might be to zero the scale, add resin then hardener so you are weighing both components. As has been pointed out, the gram or fractional gram scales give the best accuracy.
The weird pattern might be the additive. It also might be caused by different temperatures of the components after microwaving. The main thing is to stir the heck out it… several minutes is recommended. That would be several minutes after all components have been added. If the resin was really jazzed from the microwave, it might do weird things.
Do you recall how much additive you used and how it was proportioned - I.E. as a percentage of the resin, hardener or both?
I see what you’re saying John, but final weight and final volume may or may not be close enough. Sounds like the proportions are off. I haven’t checked post mixing, but 12 oz of resin by weight is likely not the same as 12 oz. by volume.
Rachel, if you use a measuring cup for resin, use another same brand measuring cup for hardener. If you mix by weight, mix both parts by weight.
The best is when you’re digi scale is running out of batteries…I’ve been in the process of measuring and i’m watching the number count down backwards on my scale…needless to say that panic ensued because i zeroed out the resin then was adding the hardener to the same container.
Absolutely… recommended ratios are 100:50 by volume, 100:45 by weight.
Even with a perfectly accurate calibrated mixing cup there is room for error when trying to ratio the components by volume (resin) and weight (hardener.) Better to stick with one method or the other but I think most believe that the gram scales work better than eyeballing to the line. I’ve tried to eyeball it while the cup is on the scale and I’m usually pretty far off in terms of weight.
Greg Loehr has pointed out that with the margin for error in his product, it would likely work out OK using 100:50 by weight but obviously if there is a problem, getting closer to the recommended ratios is a good place to start.
The best is when you’re digi scale is running out of batteries…I’ve been in the process of measuring and i’m watching the number count down backwards on my scale…needless to say that panic ensued because i zeroed out the resin then was adding the hardener to the same container.
See my aforementioned method, divide total desired number by 3.22. The total minus that answer is how much resin to pour in. The way bammbamm showed me to do it, is to pour in the hardener, then add resin until my total desired weight is reached.
It was my first time using the scale I had bought so I wanted to figure out just how much the resin actually weighs. I tared the cup on the scale and then poured in the 8oz, then did the math to get the amount of hardener. I tared the scale again and poured in the right amount. It just so happened that it came to 12 oz exactly on the side of the cup, which I think is a good way to double check.
I’m thinking the weird pattern is the additive, I’ll most likely just stop using it, I’ve never had much problem sanding without it anyway. I always stir for at least several minutes. I watch the swirl patterns in the cup and scrape the sides until everything looks clear. Have you ever noticed how you can see the hardener in the cup when you’re stirring?
I’ve found that microwaving the resin makes it a lot easier to mix too. I don’t get nearly as many bubbles because the viscosity of the resin allows them to escape faster.
Last things to try if you have the time or money. A different manufacturer of resin. Also after a trip through the archives several posters said it’s good to keep your temperature constant as possible throughout the glassing.
After a few days you may want to try post curing, if you have the equipment that is. For Resin Research resin ask Greg Loehr what the ideal time and temperature is for post curing RR if you want to go down that track.
I’m no pro but I’m up to 50 boards almost all glassed with RR epoxy. I’ve had my share of problems with contamination, srewed up glass jobs from poor mixing, and even once poured left over hardener into a half gallon of resin.
The biggest tip I can give is to develop some sort of consistent pattern that your comfortable with in mixing the different additives and components of the resin.
I decided a while ago to get a scale. 27 bucks on Ebay for a stainless digital scale that measures ounces and grams. The scale fits perfectly inside a gallon size zip lock bag and I keep a fresh 9 volt battery in my supply box for when it dies while mixing resin.
I got some syringes for measuring cc’s for the X55 and the additive f at my local pet supply store. The syringes actually make dealing with the f nice because you only use what you need and almost never spill, same with the X55 and of course you use them without the needles. Just suck up what you need with the tip. Since using the syringes I’ve less problems with f.
Probably the most helpful thing I did was to make a simple chart that I put up in my glassing room. One side is marked resin and the other is marked hardener. It starts with 1 ounce and goes all the way up to 20. Right across from the resin number is a corresponding number for hardener. I rounded all the .45’s to .5. The chart is well marked so you can’t mix numbers up, just used a highlighter to seperate the rows. The mixing table is nice because I’ve made most of my mistakes from stupid errors doing quick math in my head while I’m thinking about everything else except my grade school math while mixing.
By using the scale you have less waste and spillage. Just use one mixing bucket, zero it out on the scale and add resin and hardener straight out of the container.
I’ve tried to keep good notes so I have a pretty good system. I know just about within an ounce how much resin to use for a given board size and layup schedule.
It sounds a bit anal but now that I’ve been doing this for a while I feel really comfortable glassing, less hassles and annoying problems.
Oops, I forgot to add I take a big black marker and put a R on the resin cap and bottle and a H on the hardener. The damm containers look exactly the same. Sounds retarded, but I’ve had my moments.
Viscosity is everything. The difference of this between the resin and the hardener is the root of all problems with epoxies.
My problems with epoxy curing were pretty simple to correct (I use straight RR, no additives, all pigmented). When you weigh it, it is best to err on a bit more hardner that trying to hit the exact amount you’ve calculated. Make sure that you completely get everything out of each cup and really, really mix it using a big paint stick. Because I use color, I’m probably mixing more anyhow. I will post cure if the temp will fall below 70F, and I use the foil/cardboard “oven” and some lights. During the summer, I put the box up in the rafters and don’t use the lights. Like Stingray, I always let it go for 24 hours, sometimes up to 72 and I schedule things to allow for that. Even on my early screw-ups, they all managed to cure within a week.
I have a glassing notebook that has a bunch of notes for fin box installation, sanding coat amounts, lay-up schedules, etc. I hand wrote the table on the back cover one day because I use Fiberglass Hawaii epoxy and the RR. They both have different mixing ratios and I was sick of doing all that small math in my head. It seems like it might be hard to screw it up but I’ve done some really stupid things by accidentally mixing totally wrong ratios.
If I have time later I’ll try to transfer my notes to a table format and post the info.
That is for RR and it’s in ounces. I remembered the “func” of my calculator and sat there one day multiplying .45 into every number.
The FBH one I believe is even less with the conversion factor being .4 instead of .45.
I should put the total mixed to the far right just to really stupid proof the table but the notebook was too small.
The cool thing I found was how little hardener I needed for the big batches. Before with the graduated cups I was always over using the hardener. Now I buy a 3 gallon kit I use all 3 gallons. Also the waste factor of having material left over in seperate cups and then not remembering what was put into what is over with the scale and one mix bucket technique.
