Adhesives

You are not logged in. [ Login ] Why log in
(NOTE: Login is not required to post)

pre-mixing thickener to resin prior to adding hardener

8/7/14       
Dan Bloomer  Member

Website: http://www.handrailing.com

I just came across this portion of an old post by a contributor re. doing a larger and involved bent lam with epoxy:

"When I do large laminations, I measure out however many cups of resin I expect to need, then mix in however much colloidal silica to thicken it. The hardener can be measured by the mixing helper using the same cup over and over."

I believe the contributor is saying he's mixing the resin and thickener before adding the hardener. While this would seem to save much hassle in the midst of the glue-up it is a bad idea; West System warns against doing this. I know having done so on a glue-up many years ago. Finding a sample of the bend long after the fact I was shocked at how easily it came apart.

8/8/14       #2: pre-mixing thickener to resin prior ...
Keith Newton

Dan, that sounds like something I posted. I don't recall if I was using WEST or system 3 at that time, but I had a crew of probably 8 friends and students who were all up to speed on vacuum bagging.

Half of them had taken two classes from me, and the others were sailing friends who had worked on boats with me.

Before they left their jobs and come to my shop, I had measured the resin into about 40 clear 16 oz solo cups before mixing in the colloidal silica, so there wasn't any doubt the ratio being thrown off by adding the silica.

Once the hardener was added, it was power mixed using a drill-press with a paint mixing paddle. I had punched a hole through a plastic coffee can lid, which was on the 1/4" mixing rod above the paddle. This kept the mixer from slinging epoxy everywhere, but took a 3rd hand to start and stop, so I had two people designated as mixers.
One would measure the hardener and pour it into the cup with resin, hand it to the other, who would bring the cup up under the plastic lid, then turn on the drill press. Then he would take the last cup, and with a stick scrape all sides and bottom while mixing to make sure there were no boundary layers on the side that hadn't gotten mixed.

He would then pass the cup to me or another friend with a roller. With these small batches, we poured the mixed epoxy onto the plys ahead of the roller as we walked from one end of these 21' x 22" wide plys. This trick is much faster than having to pick the epoxy out of a roller tray. After the first run, then we went back spreading it out to the edges, rolling sideways and diagonally.

It was in the high 90º that evening, and with all of us working hard and furious, it was almost an hour after mixing our first batch, before the bag was sealed and wrapped around the form, so I was sweating bullets, but we made it.

I have forgotten how many layers there were, but the total thickness was 2". However, I left the middle layer dry, so I could rout the tread mortice all the way through the inside half, then the tread could be inserted from the outside, which made assembly easy, rather than impossible due to the changing pitch and tapper of each tread.

Here is a link to some photos of the project. Sorry I don't have and digital shots of in progress, but I recall that after the vacuum was drawn, I figured there was 80 tons of pressure on that largest part, the outside stringer. We celebrated with a few beers after that.

If you have tried this, you must measure your ratio before adding the silica to the resin. Then mixing long and vigorous enough, scraping the sides and bottom constantly so as to not leave boundary layers of unmixed resin are mandatory.

If you are sure you've done that, and still had failure, it could be due to cold atmosphere. Heat is needed to get epoxy to kick. In cold weather, I do my mixing with the cup submerged in a hot water bath, then tent my project with a tarp and heater blowing into it.

This elliptical stair was built about 20 years ago, without any callback, so I don't think there was anything wrong with my method. If you have tried this and failed, I'd be happy to hear exactly what you did, and maybe together we can figure out what went wrong.

But for me, if I had waited to mix the resin and hardener, then add the silica, I'd probably have added 30 minutes, which probably would have been too long at that high temperature.

By the way, I only use epoxy from FGCI now. It is higher viscosity, and has a 1-1 mix ratio, which is not very sensitive about being off a little. But the best part, is the price, which is about 1/2 of the ones mentioned above.

https://www.flickr.com/photos/7391658@N03/sets/72157640482388695/

8/9/14       #3: pre-mixing thickener to resin prior ...
Dan Bloomer  Member

Website: http://www.handrailing.com

I have a sense that a significant amount of resin stays adhered to the thickener particles in an unmixed state and thus the mix is compromised. It sort of makes sense that the 5 to 1 mix of the West System might be more sensitive to this condition than a 1 to 1 formula. Also the power mixing might help out.

8/13/14       #5: pre-mixing thickener to resin prior ...
Jim Baldwin

I question the necessity of epoxy. I know a lot of guys think that it is an absolute must but I think it's almost never required. The only reason for ever using the stuff is if you absolutely can't get something clamped.

From the sound of your description, it sounds like you're using a vacuum bag which should provide adequate clamping.

Convince me then that I don't know what I'm talking about. Flying stairs have been built for generations without the two-part goo.

8/13/14       #6: pre-mixing thickener to resin prior ...
Dan Bloomer

Jim,
I agree. I don't do boat work, which would incline me in that direction. Urea formaldehyde mostly or Tite-Bond Extend II or III are my choices for stringer, fascia, etc bends.

I use epoxy when joinery requires gap-filling. There are photos here of a stair we did joining straight stringer sections to curved. The joinery was done with threaded rod and epoxy set into deeply drilled holes at the ends of the stringer sections. The glue-up shown is of 24" x 5/8" rods being glued and holes being filled with thickened epoxy. The dominos are mostly there for alignment.
When the poplar stringer core was complete, we veneered it with 1/16" rift white oak.


Click the link below to download the file included with this post.

NJ_stair_glue_up_1reduced.pdf



Click the link below to download the file included with this post.

NJ_stair_glue_up_2reduced.pdf



Click the link below to download the file included with this post.

NJ_stair_glue_up_3reduced.pdf

8/13/14       #7: pre-mixing thickener to resin prior ...
Dan Bloomer  Member

Website: http://www.handrailing.com

Here's a photo of the finished stair


View higher quality, full size image (800 X 600)

8/13/14       #8: pre-mixing thickener to resin prior ...
Jim Baldwin

Wow, very nice work Captain Dan! I built stairs too and occasionally work on boats...I still however, steer-well-clear of epoxy.

West Systems stuff was originally designed for cold-molded boat construction and other non-clamped, marine applications. In this regard there is no substitute. As I'm sure you're aware though, tightly clamped stair rail or stringer bends can squeeze the thickened epoxy out or significantly reduce its' mil thickness. This can be very bad news indeed...

I personally don't recommend learning this the hard way.


Post a Response
  • Notify me of responses to this thread
  • Subscribe to email updates on this Forum
  • To receive email notification of additions to this forum thread,
    enter your name and email address, and then click the
    "Keep Me Posted" button below.

    Please Note: If you have posted a message or response,
    do not submit this request ... you are already signed up
    to receive notification!

    Your Name:
    E-Mail Address:
    Enter the correct numbers into the field below:
     

    Date of your Birth:



    Return to top of page

    Buy & Sell Exchanges | Forums | Galleries | Site Map

    FORUM GUIDELINES: Please review the guidelines below before posting at WOODWEB's Interactive Message Boards (return to top)

  • WOODWEB is a professional industrial woodworking site. Hobbyist and homeowner woodworking questions are inappropriate.
  • Messages should be kept reasonably short and on topic, relating to the focus of the forum. Responses should relate to the original question.
  • A valid email return address must be included with each message.
  • Advertising is inappropriate. The only exceptions are the Classified Ads Exchange, Machinery Exchange, Lumber Exchange, and Job Opportunities and Services Exchange. When posting listings in these areas, review the posting instructions carefully.
  • Subject lines may be edited for length and clarity.
  • "Cross posting" is not permitted. Choose the best forum for your question, and post your question at one forum only.
  • Messages requesting private responses will be removed - Forums are designed to provide information and assistance for all of our visitors. Private response requests are appropriate at WOODWEB's Exchanges and Job Opportunities and Services.
  • Messages that accuse businesses or individuals of alleged negative actions or behavior are inappropriate since WOODWEB is unable to verify or substantiate the claims.
  • Posts with the intent of soliciting answers to surveys are not appropriate. Contact WOODWEB for more information on initiating a survey.
  • Excessive forum participation by an individual upsets the balance of a healthy forum atmosphere. Individuals who excessively post responses containing marginal content will be considered repeat forum abusers.
  • Responses that initiate or support inappropriate and off-topic discussion of general politics detract from the professional woodworking focus of WOODWEB, and will be removed.
  • Participants are encouraged to use their real name when posting. Intentionally using another persons name is prohibited, and posts of this nature will be removed at WOODWEB's discretion.
  • Comments, questions, or criticisms regarding Forum policies should be directed to WOODWEB's Systems Administrator
    (return to top).

    Carefully review your message before clicking on the "Send Message" button - you will not be able to revise the message once it has been sent.

    You will be notified of responses to the message(s) you posted via email. Be sure to enter your email address correctly.

    WOODWEB's forums are a highly regarded resource for professional woodworkers. Messages and responses that are crafted in a professional and civil manner strengthen this resource. Messages that do not reflect a professional tone reduce the value of our forums.

    Messages are inappropriate when their content: is deemed libelous in nature or is based on rumor, fails to meet basic standards of decorum, contains blatant advertising or inappropriate emphasis on self promotion (return to top).

    Libel:   Posts which defame an individual or organization, or employ a tone which can be viewed as malicious in nature. Words, pictures, or cartoons which expose a person or organization to public hatred, shame, disgrace, or ridicule, or induce an ill opinion of a person or organization, are libelous.

    Improper Decorum:   Posts which are profane, inciting, disrespectful or uncivil in tone, or maliciously worded. This also includes the venting of unsubstantiated opinions. Such messages do little to illuminate a given topic, and often have the opposite effect. Constructive criticism is acceptable (return to top).

    Advertising:   The purpose of WOODWEB Forums is to provide answers, not an advertising venue. Companies participating in a Forum discussion should provide specific answers to posted questions. WOODWEB suggests that businesses include an appropriately crafted signature in order to identify their company. A well meaning post that seems to be on-topic but contains a product reference may do your business more harm than good in the Forum environment. Forum users may perceive your references to specific products as unsolicited advertising (spam) and consciously avoid your web site or services. A well-crafted signature is an appropriate way to advertise your services that will not offend potential customers. Signatures should be limited to 4-6 lines, and may contain information that identifies the type of business you're in, your URL and email address (return to top).

    Repeated Forum Abuse: Forum participants who repeatedly fail to follow WOODWEB's Forum Guidelines may encounter difficulty when attempting to post messages.

    There are often situations when the original message asks for opinions: "What is the best widget for my type of shop?". To a certain extent, the person posting the message is responsible for including specific questions within the message. An open ended question (like the one above) invites responses that may read as sales pitches. WOODWEB suggests that companies responding to such a question provide detailed and substantive replies rather than responses that read as a one-sided product promotion. It has been WOODWEB's experience that substantive responses are held in higher regard by our readers (return to top).

    The staff of WOODWEB assume no responsibility for the accuracy, content, or outcome of any posting transmitted at WOODWEB's Message Boards. Participants should undertake the use of machinery, materials and methods discussed at WOODWEB's Message Boards after considerate evaluation, and at their own risk. WOODWEB reserves the right to delete any messages it deems inappropriate. (return to top)


  • Forum Posting Help
    Your Name The name you enter in this field will be the name that appears with your post or response (return to form).
    Your Website Personal or business website links must point to the author's website. Inappropriate links will be removed without notice, and at WOODWEB's sole discretion. WOODWEB reserves the right to delete any messages with links it deems inappropriate. (return to form)
    E-Mail Address Your e-mail address will not be publicly viewable. Forum participants will be able to contact you using a contact link (included with your post) that is substituted for your actual address. You must include a valid email address in this field. (return to form)
    Subject Subject may be edited for length and clarity. Subject lines should provide an indication of the content of your post. (return to form)
    Thread Related Link and Image Guidelines Thread Related Links posted at WOODWEB's Forums and Exchanges should point to locations that provide supporting information for the topic being discussed in the current message thread. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related Link that directs visitors to an area with inappropriate content will be removed. WOODWEB reserves the right to delete any messages with links or images it deems inappropriate. (return to form)
    Thread Related File Uploads Thread Related Files posted at WOODWEB's Forums and Exchanges should provide supporting information for the topic being discussed in the current message thread. Video Files: acceptable video formats are: .MOV .AVI .WMV .MPEG .MPG .MP4 (Image Upload Tips)   If you encounter any difficulty when uploading video files, E-mail WOODWEB for assistance. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related File that contains inappropriate content will be removed, and uploaded files that are not directly related to the message thread will be removed. WOODWEB reserves the right to delete any messages with links, files, or images it deems inappropriate. (return to form)