I'm have had a few issues with my sanding coats lately (sanding coat, fill coat, hot coat...the coat immediatly following laminating...I've heard it called all of the above.) I'm using UV Cure resin. The first coat I did on the bottom of the board turned out fine. Nice and hard, ready to sand. The second on the deck never seemed to cure like it should. It still feels tacky almost like I didn't add any surfacing agent at all...but I did. I was told once that the amount of surfacing agent really isn't supper important, just as long as you have ENOUGH. If you have too little, we then you're screwed. So if anything I put in a bit TOO much. Could this be an issue? I don't take it directly in the sun once I've layed it on, I do wait a few minutes to let the wax rise to the surface like it says. I'm just kinda at a loss. Also, now I have some super sweet fingerprints on it...any way to get those out before I have to put on another coat of sanding resin?
It could be that you are not letting the wax rise during the hot coat. UV resin is very temperamental when i comes to curing in the sun, i usually add MEKP like i would normal resin and let the wax rise before i place it in the sun. If you decide not to add MEKP you have to flash the hot coat for a couple seconds then bring it inside in for about 5 mins before placing it back out in the sun. Are you mixing the UV resin yourself or using a premixed like Suncure or Solarez?
When you use UV cure resin put a little bit extra SA. you have to wait about 5-7 min before exposing it to sun. The 5-7 min starts after you do your last brush stroke of application. Another problem you could have is that the Paraffin wax in the SA solution is not dissolved. I take my can of SA and set it in a little bit of warm water. If you can see chunks of wax, then it is not dissolved. If you are using Sanding resin, with SA added already, then make sure it is room temp or warmer, but not so warm that your hotcoat drains of theboard.
Anothe little tip is to look at the wet resin right before you expose it to sun light. if you see a hazy film on the top of your hotcoat then you are okay. this means that the wax has had time to rise to the surface and is sandable.
good luck, and I hope this helps
Hi -
Just to get terminology straight (at least in my mind)...
"Hot Coat" = Resin mixed 'hot' with wax/styrene solution resulting in tack-free finish.
"Fill Coat" = Layer of epoxy resin applied after lamination. Mixed to standard proportions - not 'hot.'
"Sand Coat" = Could be either of the above.
Anyway, your problem is likely one of two things. Since your first batch on the bottom turned out OK, I wonder if you stirred the can enough before adding the surfacing agent to your resin? It is possible that the wax additive rose to the surface and got poured off leaving wax starved styrene in the can.
It is also possible that it wasn't given enough time to rise after you brushed it on. I generally give it 10-15 minutes before putting in the sun.
If you poured off most of the wax on your first batch, it was wax rich and probably didn't need much time to rise.
My suggestion would be to check your surfacing agent and see if you have some wax in it. You can usually tell if you pour it out in a clean glass jar and let it get cold. The wax will usually form a semi-solid layer at the top.
No wax or barely any? Get yourself some paraffin at the grocery store - it comes in 1 lb boxes and is quite cheap. Check the canning department.
Scrape a bunch of it in to what's left of your surfacing agent. Roughly 5-6% is about right. Heat it up slowly in a can of hot water or whatever. The wax will dissolve and you should be good to go.
I would simply brush on another hot coat. Shoot a cap or two of the recharged surfacing agent in your resin and mix thoroughly. Brush it on - directly over what is on there now. Use acetone on a clean white rag to remove the fingerprints first. Maybe add some MEKP (regular catalyst) in the mix as well.
Yep...SA had pieced of wax in it. Just heated it in warm water and layed down another coat w/MEKP. Worked great! Thanks!!
…hello John,
HC or FC is the same
HC is what most say, FC is the way Aussie s say.
.There are nuthin hot regarding a HC
I always thought it was called a HOT coat because it has extra catalyst to help it kick faster(causing heat). The quicker kick of resin would prevent resin from draining off, giving you something to sand into. Maybe this is wrong though???
Howzit astevens, No you have it right. Aloha,Kokua
…if you put too much MEKP will kick faster and with no time to the wax rise properly
Assuming the proper amount of surfacing agent is mixed well within the resin one can assure success by exposing resin for a short time to UV light and then letting the wax rise for a minute in the shade. Then re-expose to UV light for curing. It is not magic, you just have to allow time for the wax to come up to the surface- its simple…
Another tip is to mix the UV-pixie dust into the surfacing agent before mixing into the resin for equal dispersion. If it did not rise the first time reshoot it with a thin coat or you will gum up the paper, but if you do not do this and go straight to sanding wet your sand paper with a bit of acetone and it will help it not do gum. But remember acetone is highly flammable, and I recommend another hot coat, sand coat top coat or fill coat, whatever you want to call it…
Here is the issue, if you added you sanding solution, or have the premade UV cure resin. When you hot coat expose your hot coated board to your uv source for about 15 sec-20 sec. Then bring away from UV source. Let the board sit for about 2 min. This will allow the wax to properly rise to surface. If you don’t do this, the wax will get stuck in between and youll have a tacky surface, very much like a normal lam resin.
Last post was closest. Just a few seconds in UV and then back inside until it starts to look milky or hazy. Then back in the UV to cure hard. Like someone said it's not magic. If you don't let the wax rise, you are basically trying to sand lam resin,which is manufactured to STAY tacky. If you are not using a UV box(which is more controlled) and the conditions outside are not bright or direct sun it may take more than a few seconds outside. Certainly no more than 20 or 30 on an overcast day. A re-hotcoat is the best remedy for one that doesn't set. Shake your can or bottle of surfacing agent/wax real good and stir your resin well. If things aren't mixed well anything can happen. Boiling and heating stuff that flamable is asking for it. Can we say "flash-point"?