Silmar bubbles

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MaxBond

Member
Joined
Jul 9, 2012
Messages
4
Location
Nashville, Tennessee
Hello, I'm new to the forum - first post. Im pretty new to turning - I've turned about 15 wood pens and have just attempted making my first PR blanks. Actually I used Silmar 40 (not 41). When I went to turn the blanks, I found there were bubbles in the blanks, resulting in holes. I didn't expect that. Any ideas what I did wrong? Also, for those of you that use Silmar, what type of mask (if any) did you use to avoid the fumes?
 
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Either your mixing process incorporated air into the resin or there was some moisture present.

Where you casting something or mixing colors? Need more info to get to the bottom of it.
 
I wear a 3M organic vapor half mask. Cost about $30. I also wear wrap around safety goggles and nitrile gloves.

Mixing will introduce bubbles no matter how careful you are. You didn't mention using vacuum or pressure.

Vacuum can be used to degas and completely eliminate any air in the resin.

Pressure can be used during curing to shrink the bubbles to a size where they are hopefully not noticeable. The pressure must be maintained until the resin is fully cured.

I've never tried mechanical means of dealing with bubbles (ultrasonic vibration or physically moving the bubbles to a waste area of the cast with small implements).

I prefer vacuum when working with PR resins.

Silmar 40 has a shorter working time than Silmar 41 (40 is almost twice as quick to gel). Silmar 40 may not be your best choice for your first casts. You will need to be quick about getting the resin in the molds and dealing with the bubbles.

Ed
 
You may have waited too long to start mixing the two colors of polyresin. I think you trapped some air between the two strata of PR colors. Even though the PRl was almost jelled when you started pouring it would have been farther along when the pour was completed. Timing is a key factor. Once PR starts to jell it gets there quickly.
Do a good turn daily!
Don
 
Great thoughts. I'm actually in the process of making a vacuum chamber, so I'll have to try that on one of the next batches. Really appreciate the thoughts on this!
 
I think your entire problem comes from using the wrong resin ( 40 years in the boat and yacht business).

Silmar 95ba-40BA (which is what you used) is meant as a STRUCTURAL fiberglass repair resin. It was designed to "patch" boats and yachts in places that wouldn't be seen, but would have amazing strength properties (In essence, it's "fast cure" Silmar 404).

I don't think there is anything you can do to reduce bubbles ins Sil95. It's a patch material (much like Bondo).

Additonally, EVEN IF YOU COULD cast 95B without bubbles, it will yellow much like epoxy resin.

Edit: I just noticed that you are from Nashville, Tn. Go see Fred or Goofy ( I think Goofy has already retired) at Ebbtide Boats in White Bluff, TN-not far from you). For 2 twelve packs and 4 tacos they'll teach you everything you'll ever need to know about Silmar resin.

Respectfully submitted.
 
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