I 've been doing all my hotcoats with pre-mixed sanding resin in the past but i picked up some styrene monomer SA and decided to give it and lam resin a whirl this time.
is the 3% - 5% SA/resin ratio on the can realistic from everyones experience?
Is the SA/resin ratio temperature dependant?
Why do i hear of “thinning” resin with SA? What does that do? Make it glossier?
Thx and sorry for the irritating questions. I really do appreciate the great advice I keep getting here.
styrene monomer is the thinning agent…helps the resin to flow more smoothly…easier to work with
Interesting. The product is called “Surfacing Agent” and says on the label it “contains styrene monomer”. I bought it from fiberglasssupply.com On the can it says to add “1-2% for final coat to eliminate surface tackiness and 3-5% for sanding coat”
Surfacing agent is a solution of styrene and wax ( 1 part paraffin to 9 parts styrene). Styrene by itself, as pointed out by soulstice, is a thinner. Styrene by itself is often used to thin down laminating resin to make a gloss resin to which surfacing agent (styrene and wax solution ) is then added. Hope this helps. Patrick
thx patrick! do you typically mix the SA and Lam resind right in the cup to do a hotcoat (stir in like cat.)? No reason why it would have to be done ahead of time or in larger batches?
Mix it up as and when you need it, just like like the cat.
Also S.A. itself is not temperature dependant but the catylist is, the wax in the styrine rises to form the surface, to allow time for this to take place don’t kick the batch too fast.
Howzit mitchell, Just make sure you mix the SA in real good since it has a tendecy to float on top of lam resin. I usually stir it in by forming an eddy with a stir stick in the middle of the mixing cup so the SA is drawn downwards in to the resin. I may be wrong but sanding resin costs the same as laminating resin so if you are into premixing for later applications why not just buy sanding resin since buying the 2 chemicals separatly would cost more. Just my thoughts on the subject. Another factor to remember is styrene is very dangerous stuff and is a cancer causing chemical, so be careful when using it.Aloha,Kokua
I may be wrong but sanding resin costs the same as laminating resin so if you are into premixing for later applications why not just buy sanding resin since buying the 2 chemicals separatly would cost more.
Kokua - hello from the land of 40 degree water ;( (although I did get out to Oahu last month!) Your absolutely right…they cost the same. My reasons: just to learn something new i thought i’d try it. And i make so few boards that it seemed easy to buy a gallon of lam resin + SA and just go through it.
Mitchell,
Yes, I typically mix lam. and SA to make hotcoat resin - don’t forget to add the cat. last - otherwise it will be hell to cleanup.
If the price is the same, purchasing both lam. and hotcoat would be the way to go. Since building is a hobby, it makes more sense for me economically to buy one pail at a time - less chance for the resin to age.
As Kokua mentioned styrene is a bad actor for the body and the environment. The less you have to handle the stuff the better. So, on second thought, I would suggest you not make your own SA. Besides the melting point of wax and the vaporization point of styrene are relatively close. Great care should be exercised.
While using styrene to thin hotcoat resin will make an adequate gloss, it would be better to just buy gloss resin. Styrene tends to make resin brittle if to much is added to regular lam.
Whatever you try be very careful - wear gloves, a mask and eye protection.
Hope this is of some help.
Patrick
3% is my favored amount for hot coats. Recently I’ve been thinning with about 5% styrene plus 3% W&S for glosses with good results. I plan to do a kokua brew soon. On one of my boards to get the feel first. platty.
Here’s my scenario: I only buy UV lam. Used to also get finish resin, but I use so little and so infrequently that it would go to crap in the can.
I mix my own SA, about a half pint at a time, by shaving parafin into the can full of styrene. Shake it some, then leave it in the sun for long enough to completely dissolve the parafin. I haven’t measured the amount of parafin I shave, maybe I should, but it works, and I haven’t a sensitive scale, so my take is that it really doesn’t matter.
For longboard hot coats, I shoot a syringe-full of home-made SA into about two cups of lam resin, stir, wait a bit for the bubbles to rise, pour it on, spread, long-stroke, cross-stroke, feather stroke, and let it sit for ten minutes and the wax to rise. Then out into direct sunlight, and almost immediately I pull the tape as the resin sets. Once around with the surform to trim the resin at the tape edge.
BTW, UV cure goes off so fast that I can use cheap tape, not the expensive Scotch 233, for hot coats AND finish coats. Hell, I can, and do, also use cheap tape for cut laps! Once in a while (if it’s cloudy out) the styrene in a hot coat or finish coat will make the tape leave some adhesive on the rail; I just rub it off with my thumb.
Hobby builder here, too. I buy only uv lam resin and mix SA for my hotcoats. The reason is when I bought them separately I always use more lam resin than hot coat resin. So, I would always run out of lam and have a bunch of hotcoat resin laying around. Since mixing my own my hot coats seem to sand easier and I no longer run into gummy hotcoat scenarios. I also shoot my hot coats with a bit of catalyst to avoid this, too, even though I use the UV stuff. I think I learned that tip from Kokua. Mike