how to mix large batch of epoxy with silica

bigbad4cyl

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im doing my curved transom soon and am going to be using the west system epoxy with the silica ,to fill the void ,,,,im thinking ill need a large amount of epoxy filler so how do i mix a large batch like that ....im hearing 1 to 1 ratio of epoxy to silica.....should i pre mesure the hardner and epoxy and silica in seperate containers then mix it all in a 5 gallon bucket....
 

Pun

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Re: how to mix large batch of epoxy with silica

Always mix your epoxy and hardner first before adding filler. Larger batches require up to 5 minutes of thorough mixing. Mix slow enough to not introduce any air bubbles. <br /><br />Keep in mind that epoxy resin has a fairly short pot life. Depending upon the type of hardner you're using and the temperature and humidity in your work environment, accuracy of mix and other variables, this pot life may vary. Nevertheless, I would consider mixing up no more than a half to 3/4ths of a quart of resin at one time.
 

crab bait

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Re: how to mix large batch of epoxy with silica

i wouldn't mix up a large batch..!!<br />cause the more volume you have ,, the more heat,, the shorter the pot life..<br /><br />an you'll already diminish alot of that time up in the mix..<br /><br />use many small batches a quart or less..i'd go with a pint.. un-till you get feet wet..
 

Realgun

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Re: how to mix large batch of epoxy with silica

Do yourself a favor wear a dust mask as that silca goes everywhere and into your lungs to.<br /><br />I prefered the milled glass fibers as they were easier to use and they have more strength.
 

bigbad4cyl

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Re: how to mix large batch of epoxy with silica

i got alot of the 406 colloidal silica from west marine....i dont see milled glass from west marine...
 

Boomyal

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Re: how to mix large batch of epoxy with silica

Mix in the filler until the resin is the consistancy that you want it. Then get it out of your pot in a hurry. Don't bother to try to apply it with any accuracy, just slap in on and spread it so that is no more than 1/2" thick. Once done you'll have plenty of time to work it.<br /><br />Ohyeah, as stated above, mix the hardener and resin thoroughly before adding the thickener.
 

BillP

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Re: how to mix large batch of epoxy with silica

Thickener ratio depends on the viscosity of your particular resin...1:1 is a good starter but you may need more silica to keep it from running. Epoxy resin gets thinner as it starts to kick off so you have to mix the thickener more than first glance will tell you would work. Like already posted it makes the pot life short. I personally don't worry about air bubbles, it takes too long to stir without getting them. <br /><br />In really hot weather I cool the hardener before mixing and it extends the pot life. You normally double/reduce the kick time with every 10 degree change in temp...up or down. Cooling makes the resin thicker and more difficult to mix too.
 

craze1cars

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Re: how to mix large batch of epoxy with silica

Frankly I think if you mix such a large batch as you're considering (in a 5 gallon bucket?), AND add a bunch of silica, you're going to end up with a mixture that gets so hot it'll literally melt the bucket. Then you'll have one HECK of a mess. That stuff gets really hot. And the more silica you add to make it thicker, the hotter it will get. I speak from experience and am not exaggerating...I have melted some containers even with small batches when I found myself taking too long to work. This is most common with a high silica content when I'm trying to make a peanut-butter consistency mix for filleting. Here's the formulas I learned once the hard way...More silica = more heat. More resin = more heat. More silica AND resin = melted bucket and burnt hand.<br /><br />Do it in small batches, you'll be very sorry if you go too big. As for a ratio, just keep adding silica until it gets as thick as you want it for your application. There's no fixed rule. I think you'll find you need more than 1:1 silica/resin ratio, but I'm not as familiar with West's, as I use Raka. I'm sure they're similar. For example, my peanut-butter thick mixture I make for filleting can approach 10 to 1 (I think), but I never measure it to know for sure...I just keep dumping it in and mixing until it's thick enough for whatever I'm doing.<br /><br />If this is structural, I agree with the stir FAST theory to help save working time, who cares about air bubbles? But if this is cosmetic, that's a different story and you'll want to stir slow for a smooth mixture. Good luck!
 

18rabbit

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Nov 14, 2003
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Re: how to mix large batch of epoxy with silica

The milled glass fibers Realgun was mentioning, and chopped fibers, are available from here.<br /><br />You'll also find other fillers as well as silica for less than West Systems typically sells at...for a future project, of course.<br /> :)
 

bigbad4cyl

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Re: how to mix large batch of epoxy with silica

well what can i buy at west marine by next weekend ,,,,im trying to fill the gap between the transome skin and the new wood i cut for the transome in 3/4 inch marine grade plywood...i got some alrod and vaius washers and plan on using the outdrive mounting holes to suck the wood up against the fiberglass ,,,also use all thread through the drain plug area and on the u bolt eyes.... i hope this will be enough as i dont want to drill a bunch of holes ....after this cures ill put my next layer of 3/4 marine against the other with ss <br /> screws sucking them tight and glasing over the screws with epoxy /cloth ............................................................any way what wouould be good to mix with the epoxy/silica to fill the gap back there im now thinking 404 high density ,,,from west systems ,which i have axcess to...
 

MercMark

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Re: how to mix large batch of epoxy with silica

Mix in small batches.<br /><br />Like it says above, I nearly burned my hand when my first batch kicked on me while I was trying to mix peanut butter. The thicker it gets, the less it conducts heat out. As you thicken West Sys with 406, it starts to behave more like a hot mix of polyester resin. I had a spot in my layup where the filler go a little thick and I thought I saw it give off a whisp of smoke. I spent the next 1/2 hour with aching hands from holding ice against the hull.<br /><br />I ended up buying a metal paint tray to mix thick stuff in. I left it as spread out in the pan as I could when it was mixing too.<br /><br />I think if you try and mix a huge bucket, you'll end up with a fire.
 

bigbad4cyl

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Re: how to mix large batch of epoxy with silica

oh i wasent going to fill the bucket but it sounds comical.
 
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