Worthless Wood Question

[PTownSubbie]

I have been giving the worthless wood thing a try. My question comes from the curing of the wood and PR.

I use PR and oil based gel paint as the coloring. I prep the PR and pour it into the mold with the piece of wood. When I put it in my pressure pot, the mold is fully covered and full. When I pull it out the next morning, it is no longer full and the wood is not fully covered.

Has anyone else had this happen? Is the pressure forcing that much PR into the wood? I pressurize to ~70 psi and it stays there for usually about 8-12 hours.

The PR is not fully cured either. I don't do anything different with the amount of MEKP than when I do straight PR. The only difference is I don't use the pressure pot when I do straight PR.

 

[NewLondon88]

Depending on the types of PR and oil paint, they may not be compatible. I don't
know that for sure, but it's possible that the oil is inhibiting the crosslinking in the
resin.

And depending on the wood type, it could certainly draw in fluids, especially the oil.
But have you checked to see if it is the liquid level dropping, or is it possibly the
wood floating?

Just guessing, here. I haven't run into this before..

 

[PTownSubbie]

Charlie,

It is definately not the wood floating because I glue a piece of scrap wood to the top and then place tape over the scrap to hold it into the mold. Learned that trick from the Library tutorial.

The PR is definately going somewhere. The only thing I know is that it is not the bottom of the pot. I can only guess that it is being driven into the wood. The wood is Jarrah and has quite a few checks and holes but not as much as what I think I am loosing.

I have done 5 pieces now and each one seems like it is just sucking up the PR.

As for the oil based paint, it desolves much easier in the PR and I don't have any problems with it until I use the pressure pot. I took the last batch out and it was still tacky 12 hours. I didn't know if the lack of air changout could be causing some weird reaction.

 

[leehljp]

I haven't done any 'worthless wood' PR casting but I have done stabilizing and PR + coffee and a few other materials. Most woods can be from 10% to 40% air. Vac or pressure will cause more PR into the spaces.

I have found that I really need a mold that is not 'square' but rather 1/"8 to 3/16" deeper than it is wide to allow for the shrinking effect of the PR that takes place after the molds are full. I have several coffee and other PR blanks that are only fit for slimlines or other smallish diameter pens. I must note that I don't use the same kind of PR as available in the US and it is possible that my problem is from the Japanese brand that I am use, but it does sound similar to your problem.

 

[Klanham]

Absolutely seeing the same things Fred. I cut a piece of 1/2 UHMW and ran drywall screws through it in four spots. That goes on top to hold the wood down so it doesn't float. Pressure over night at 60 PSI and the next morning anywhere from 20 -30% "shrinkage" and noway is it cured. Still very soupy on the bottom and so sticky everywhere else you can't handle it out of the mold. I use powdered pigments from Artstuf so I don't think it's the oil colors but it may well be the oil from the wood. What kind of wood are you using? I seem to have more problems with "oily" woods line Rosewood. Plan to try to less oily like a cherry and see what happens.

Keith

 

[ngeb528]

I had the same thing happen and left it in the mold (out of the pressure pot) for a couple of days. That helped the top become less tacky.

When I popped it out, there were still tacky areas so I set it out on the screened porch for a few days more and it was fine after that.

I think the PR reacts to some types of wood more than others. I did two different woods in one mold and the amboyna burl side cured faster than the water oak side.

 

[JohnU]

Pr will usually come out tacky. All of my cast do and I just pop them out of the molds and let them sit in the sun for a few hours outside. Works every time. Also, pr will shrink when it cures. Ive had pr pull away from wood also, but its usually on the bottom or outter sides of the molds where its thin and not needed. Try heating your worthless wood in the oven for a while on a low heat before casting. I pour mine and let it sit all night in the pressure pot before messing with it. Pr is needs time where aluminlite is quick. Ive had great luck with osage, elm, buckeye and oak but never tried the oily woods, so I cant comment on if that causes any problems. Good Luck and Dont Give Up!

 

[its_virgil]

Alumalite may be the better choice for worthless wood castings...adhering to the wood is one major reason. Alumalite seems to "stick" to the wood better.
Do a good turn daily!
Don

 

[workinforwood]

Yes, I too find that not only does alumilite stick better for worthless wood, but it doesn't color bleed. A lot of times with PR I find that the paint seems to bleed into the wood and that can be pretty ugly. The alumilite chemically bonds to the paint and it also cures so fast that there isn't time for any paint colors to soak into the wood. Sometimes with alumilite, I find the mold is slightly less full than it was, and sometimes it's visually the same..some woods penetrate better than others.

 

[GouletPens]

You're experiencing one of the many reasons why PR is not ideal for WW casting. Alumilite is really the way to go here for many reasons. Yeah its a little more expensive and whatnot, but you don't get the sloppy mess you're dealing with in this post. The last couple of posters have mentioned a couple of reasons why PR's not good for WW, and here's another one. The PR shrinks a bit as it cures which is great if it's just PR you're casting b/c it'll pull away a bit from the mold and be easy to remove. But with WW, it's shrinking and pulling away from the wood as well. If you cast WW in PR and turn it, you'll find you'll have chunks of PR blowing out and chipping out all over the place and it'll be a hot mess. If you seek to understand why the PR is magically disappearing, that's fine, but even if you fix the problem there's still a host of other issues that make PR better left on the shelf for WW casting. Go get yourself some alumilite. IMHO:biggrin:

 

[jkeithrussell]

Can you color Alumilite with the same pigments and powders that you use for PR?

 

[PTownSubbie]

Thanks for all the info on PR vs Alumite. I posted this because it is something that I hadn't seen with just straight up casting.

The loss of PR volume just seemed excessive to me and I didn't know why. I think many of the statements made here have helped me understand where it is going and that maybe I need to venture into the Alumite scene if I want to continue with WW.

Thanks for all the input!!! I love this site!!! The knowledgebase here is incredible.

 

[NewLondon88]

Can you color Alumilite with the same pigments and powders that you use for PR?

You can use the powders, PearlEx and such .. but probably not the liquids.
TransTint will work a little bit in small quantities, but maybe not on all
colors. Some colors seem to react differently, I don't know why.

Liquid dyes for PR will likely just bubble or give you pinholes. Pinholes are
the step just before foam. Mixol is something I've tried once and I only used
one drop for about 6 ounces of Alumilite. I got pinholes, so two drops might
have given me a tray of foam. I didn't go further.

Probably not the Yes/No answer you were looking for.

 

[GouletPens]

You can use the powders, PearlEx and such .. but probably not the liquids.
TransTint will work a little bit in small quantities, but maybe not on all
colors. Some colors seem to react differently, I don't know why.

Liquid dyes for PR will likely just bubble or give you pinholes. Pinholes are
the step just before foam. Mixol is something I've tried once and I only used
one drop for about 6 ounces of Alumilite. I got pinholes, so two drops might
have given me a tray of foam. I didn't go further.

Probably not the Yes/No answer you were looking for.

Not to contradict, but I actually have had success with Mixol in alumilite. I used probably 4-5 drops per ounce..I was casting one blank at a time and used what must have been 20 drops or so in the 3 ounces of alumilite. I didn't have any bubbling whatsoever, and in fact the blank turned out quite nicely! Maybe there were other factors in play with your casting. Perhaps the wood was a little wet still, as moisture is the enemy for alumilite. You have to make sure the WW is BONE dry before casting. Moisture in the wood would certainly give you bubbles.

 

[LandfillLumber]

I use mixol(well I have black and blue so far),I use them in a urethane resin that is not Alumilite but nearly the same.I have never had any issues with bubbles from it,I did get a crazy foam pour once but still have no ides why,I think some moisture got in the mix some how???I like the mixol as I can be some what consistent with the drops,my paste colorants I use a pop sickle stick and just wing it.GouletPens makes a good point in his first reply to this post as to why PR is not great for casting with wood.Chucks can fly I have done it,but with urethane's this is not an issue.Onlt down fall so far for me with urethanes is the lack of a high gloss look,I have yet to try Alumilite at all so have no clue how they shine up.Good Luck,Victor

 

[workinforwood]

I just use oil base paints for the solid colors I need. It's the cheapest way to go. $9 for a quart. You buy just the primary colors plus black and white and you have almost every color there is.

I agree with polular concensus that alumilite doesn't shine as well. The CC alumilite is more than satisfactory though, far better than the original product. But..with worthless wood, it isn't important how good a shine is anyhow, because you have to put a finish on it to protect the wood.

 

[jason_r]

Can you color Alumilite with the same pigments and powders that you use for PR?

That depends on the pigment/powder.

My resin color library has examples of things that worked, and you can read the warnings about ones that didn't.

 

[lundebc]

What exactly is worthless wood casting? I know my newbie status is shawing, but I am not sure I understand. Are you using wood that would otherwise be un-suitable for turning? Then embedding the wood with PR (or Alumilite) with the pressure pot? I've seen many threads but have not exactly understood.

Bruce

Katy, Tx

 

[jason_r]

There's a great article explaining it in the library.