Slow Curing Resin

[Bill Arnold]

A couple of days ago, I did a small test using TransTint black dye in about 3oz. of PR. I used 5 drops/oz of the MEKP. When I checked the next morning, the block was a little sticky on the surface when I pushed it out of the 1.5" PVC form I used.

My next attempt at casting began late yesterday. I had four 3/4" square by 5.25" long "worthless wood" blanks I had stabilized that I wanted to fill with resin. I mixed a total of about 10oz. of resin and added 5 drops of MEKP per ounce of resin. Our temperature has been around 80° with about 60-70% humidity. I put the blanks with resin in my pressure tank around 4pm Thursday. This morning, the resin had hardly thickened at all. So, what can I do now?

 

[BSea]

I'm guessing that the resin is silmar 41 based on the fact you said 5 drops of MEKP. It may be that your MEKP is old. I was talking to US Composits, and asked about shelf life of MEKP. The guy told me to shake the bottle. If bubbles stayed on the surface, and didn't pop immediately, then it was still good. If they pop right away, the ether has evaporated out, and it's not good any longer.

The other thing is what you used to tint the resin. In the 1st example, you said you used trans tint dye. If it's the stuff from US Composits, then you should be good to go. Since it's just tacky, about 30 minutes in a toaster oven should do the trick.

I've never used PR on worthless wood, so I won't be much help. But one thing it might be is moisture. even though your humidity isn't really to high for casting, air from a compressor has a lot of moisture. It's possible that it's introducing too much moisture. Just a guess. My next guess would be your wood wasn't completely dry.

 

[glenspens]

Just done some worthless buck eye wood with pr w/dye i used 7 to 8 dropes per oz under pressure they came out ok. mixed tue night took them out of pot wed night. also i put the leftover in 3/4 pvc no presure it came out ok. mek 2 mo old + -

 

[PSNCO]

Have you used the TransTint black dye in PR before? If not, perhaps it doesn't play nicely with PR. BSea hit on the other two likely culprits. I've had MEKP go bad from sitting in extreme temp changes. It wouldn't thicken in my cup after 30+ minutes. Grabbed a new bottle of MEKP that I had on hand and fired right off. I've had a cup of resin that got a little water in it and wouldn't harden all the way around until the water evaporated out a colple weeks later.

 

[Bill Arnold]

The reason I did a test a couple of days ago was to see if TT dyes would work with PR. It appears that is not a problem. My test chunk was done in a piece of 1.5" PVC that I had cut for bottle stoppers. That piece cured just fine so I think I'm OK using that combination. The reason I used TT dye is that's what I've used for flatwork pieces and I have a stock on hand.

The variable I introduced yesterday was the dogwood pen blanks I stabilized last week. After soaking them in CJ under vacuum overnight, I baked them at 200° overnight. The wood was dry when I started stabilizing them and appeared to be dry when I poured the resin over them, but I didn't measure the MC with my meter. Looks like I need to check some other pieces I stabilized to see if MC is an issue.

 

[Jim Burr]

It's normal for PR to be tacky on the surface when it's cured; toaster oven for 10-15 minutes at 150*'ish or just let it sit on the bench for day or 2.
PR isn't the best choice for WW. Since it shrinks as it cures, it can, and usually will pull away from the surface regardless if pressure was used or not.
Alumilite could be a better choice for WW casting.

 

[Bill Arnold]

It's normal for PR to be tacky on the surface when it's cured; toaster oven for 10-15 minutes at 150*'ish or just let it sit on the bench for day or 2.
PR isn't the best choice for WW. Since it shrinks as it cures, it can, and usually will pull away from the surface regardless if pressure was used or not.
Alumilite could be a better choice for WW casting.

Thanks, Jim. I'll get a jug of Alumilite for future wood applications. I'm on the very front end of the learning curve, as you can tell.

 

[Jim Burr]

It's normal for PR to be tacky on the surface when it's cured; toaster oven for 10-15 minutes at 150*'ish or just let it sit on the bench for day or 2.
PR isn't the best choice for WW. Since it shrinks as it cures, it can, and usually will pull away from the surface regardless if pressure was used or not.
Alumilite could be a better choice for WW casting.

Thanks, Jim. I'll get a jug of Alumilite for future wood applications. I'm on the very front end of the learning curve, as you can tell.

At least you're trying Bill!! Anything I can help with...you know how to find me!

 

[Bill Arnold]

At least you're trying Bill!! Anything I can help with...you know how to find me!

Yep. You can run, but you can't hide!

Update: I went out to my shop to check a couple of things. The MC on the dogwood I'm working with ranges from 6% to 10%. Earlier, I had put the pen blanks with resin in my toaster oven at 150° for 30 minutes. The resin is firming up, so I put it back in the oven for another half hour. I'll check it later.