What Happened ????

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RDH79

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I just pulled my first batch of pr blanks from the pot. What did I do wrong?? They are full of bubbles. I mixed as directed and didnt stir it alot. Pulled in a vaccumn over night. Do you think I added to much hardener. Check out the pics. Dont mine the color I didnt add enough coloring. Thanks Rich H.
 
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I may be way off on this, but you pull vacuum just to get the air out, then actually let it harden under pressure. If the blanks are more opaque then clear you shouldn't need to vacuum, just cast under pressure. You may have also added too much hardener and the blanks set before they were done de-gassing.
 
That would be my guess too, but given these are plain castings, I don't think they need anything but pressure (if that), and that's just for a little while, not overnight.
 
As they say, vacuum for a few minutes then switch to pressure.

But you have more than that going on. What did you use as colorant? Moisture (water based) of any kind will cause bubbling.

GK
 
My (limited) understanding is that you really want to start with vacuum if you are stabilizing or casting objects in the resin. I believe that if you are only casting resin all you should do is pressure, unless the vacuum for a short time pulls the bubbles out (but I'm not sure).
 
Vacuum helps to get the resin into tight spaces (like holes in wood) and in getting rid of bubbles. It does both by expanding the bigger areas of trapped air until it bursts. Then you release the vacuum and only the tiniest areas of air are left behind and the resin is pulled into those left over spaces. But if you leave the vacuum applied then all the tiny bubbles that are too small to be burst are expanded and held expanded until the resin sets. If you, instead, release the vacuum shrinking those tiniest bubbles back to normal size you get very small bubbles only. And if you then apply pressure the tiniest bubbles are compressed to "invisibility" and the resin is pushed the rest of the way into the cracks and crevices.

So, when do you NEED vacuum? If you have stirred in lots of air during your mixing; if you are trying to do a composite blank where there are lots of nooks and crannies to try to fill with resin; if you are trying to stabilize wood so you need the wood to "suck" the resin deep into itself (in this case you probably want to due several vacuum/release/vacuum cycles followed by as much pressure as you can safely apply).

When CAN you use vacuum? Any time you have the time before the resin begins to set. Alumilite makes vacuum almost impossible because it begins to set so quickly.

GK
 
I would definitely skip the vacuum unless you have a TON of bubbles from mixing a difficult-to-mix material.

When I do use pressure, I pressurize up to 60-70 pounds (for no other reason than I can) but most guys here say they use 20-30. I figure, if a little pressure works, a LOT should work fine, and so far it's been good to me.
 
I use no pressure or vac (I'm not set up for it) and stir with a modified spade bit in a drill. 10 drops of catalyst per ounce and I'm not having any bubble issues at all.
 
Russianwolf said:
I use no pressure or vac (I'm not set up for it) and stir with a modified spade bit in a drill. 10 drops of catalyst per ounce and I'm not having any bubble issues at all.
Click to expand...

Ahh.. but at what temp and size of cast?

If I tried casting w/ 10 drops/oz in my garage now I doubt a 4oz cast would make it out of
the cup. (~95+ degrees out there in the evening here in AZ).

I normally use ~4 drops/oz. On my most recent cast where I was doing a 16oz swirl
mixed as 2 8oz cups I used 2 drops/oz and still had it gel in 20-25min.
 
Wow Thanks for all the info. I had thought that pulling a vac would pull out and air that was in the resin. I think I had a couple things that was mentioned happening to these. I will have to check the dyes that I was using but they were with the resin I bought at Micheals. And I probably put to much hardener. I think it was 5 drops per oz. I think I was expanding the bubbles as it was setting up.
Now what does pressure do to the resin?? I would think that would hold the bubbles in if there were any.
I guess this is not as easy as I thought it was. But I will not give up.
I'm back to the garage to try some of your suggestions. Will let you know tomorrow how my second attempt turns out. Thanks Again Rich H.
 
RDH79 said:
Now what does pressure do to the resin?? I would think that would hold the bubbles in if there were any.
Click to expand...

Read the response from gketell. It tells you what the pressure does to the resin.

5 drops/oz should be OK. If you want data on volume/dye/temp/catalyst amount/gel_time check out
my color library .

It's mostly aimed at colors, but the notes include data on catalyst amount, temp, and gel time so you can have some hard data to help you along. And there's a standing offer to add recipes you send in to the library.
 
I don't use vac and very seldom use pressure when making color blanks , only for clear casting . I let my color mix sit for an hour or so before I add the hardener to let the bubbles float to the top and very seldom have any problems , and only use 3 drops per oz (depending on the temperature) so it takes some time to set up , giving any bubbles in the mold a chance to rise as well .
 
What the...

Oh... you're using IE. One of these days I'll remember to test my pages in other
browsers than Mozilla/firefox.

I'll try and get it so it renders better. It appears IE isn't recognizing
one of the formatting attributes. The center colum is supposed to be
40 characters wide.

Thanks for the heads up. It's not very useful if it's not readable.
 
shull said:
jason_r said:
If you want data on volume/dye/temp/catalyst amount/gel_time check out
my color library .

The data seems to be real helpful but just FYI I just tried to check out your color library. Several pictures were not displaying and the data seemed to be all bunched up into one column.
Click to expand...


Checked out your color library........nice!

Went to your home page.....I liked it.........your 'homepage collage' link is broken....no pic!

I gotta get busy on my website....
Click to expand...
 
titan2 said:
shull said:
Checked out your color library........nice!
Click to expand...

Glad it's of use.
I'm amazed nobody told me about the IE issue sooner on the color lib.

And remember: send me your recipes w/ pictures and I'll add them to the library.
See #60 and 61 for 2 of GlassScratcher's.

Went to your home page.....I liked it.........your 'homepage collage' link is broken....no pic!

I gotta get busy on my website....
Click to expand...

*sigh* I wonder when that broke.

But since that collage is ~7yrs old and out of date, maybe not a bad thing.

Thanks for the note.
Click to expand...
 
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