# Interesting expirement- DIY accelerator



## thefinisher (Sep 2, 2011)

So today I stopped by my local supply house and tried to pick up a couple bags of 5 minute as this is all I use for patches and such. Turns out someone came in and bought 50 bags to do a house ..... So I had to settle for a bag of 20 minute which I hate waiting around on to set. On my way to go do some patching I remembered that there are some accelerators out there for plaster that should work for durabond also. I did some research and saw USG lists "Alum" catalyst as one of their accelerators. From making homemade pickles before I know you can get "alum" in the spice isle at a grocery store. So I stopped in at my nearest grocery store and picked up some and went on to do my patches. Haphazardly I mixed up some alum in my water before adding my 20 minute in hopes of it setting faster. It turns out the grocery store stuff works great :thumbup:. I noticed that it mixed up way more creamy and almost made it slide around like plaster does but in a good way. Set time was approximately 12 minutes or so. These patches were also done over an eggshell paint which if you have ever done so you know the feathered edge of the mud takes a long time to set up than the main body of the patch. This seemed to have been eliminated with they use of alum which was quite surprising. So now being back at my house I decided to do a quick tests to determine the actual effectiveness of alum in varying degrees. For a control I mixed up standard 20 minute, secondly I used 1-1/2 cups of water and mixed 1 teaspoon of alum in my water before adding my 20 minute powder, and thirdly I mixed approximately 1 ounce of alum into roughly 1 gallon of water and used this to mix up the 20 minute. The regular 20 minute took 29 minutes to start firming up and 33 minutes in total until it was fully hard. The second mix took 9 minutes to start firming and 13 minutes to fully harden. The third mix took 17 minutes to start firming and 21 minutes to fully harden. As you can see the higher ratio of alum to water in my second mix made quite the difference. Actually the difference to the 20 minute mud control was a full 20 minutes! I did all this outside at 62 degrees and cold water on a scrap piece of rock using National Gypsum quick set lite. NG's quick set in my experience only sets at its recommended time when the temps are in the 90's so in cooler weather it is much slower. I know this isn't ground breaking or anything but I did find that the alum may have some use in my tool box... especially the part where the edges set up over paint!


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## MrWillys (Mar 10, 2014)

Interesting, we added alum at the nozzle when spraying fireproofing. I should add it was liquid from a drum with a paddle in it.


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## Mr.Brightstar (Dec 2, 2011)

Interesting indeed. 


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## MrWillys (Mar 10, 2014)

http://www.homedepot.com/catalog/pdfImages/ab/ab8a9f70-3a94-475b-b5d7-7030673c1d13.pdf

My cubby would add it to hot mud also. It came in bags but this is shown in buckets.


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## icerock drywall (Nov 13, 2010)

I just did a job yesterday. I used 20 with dirty water did 3 coats one day. I can turn 45 into 20 the same way


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## endo_alley_revisited (Aug 9, 2016)

Sometimes powdered gypsum is used as an accelerator for plaster. I have used a sure-form to scrape sheet rock dust into my mud. That sets durabond up a little faster also.


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## pytlik86 (Sep 3, 2016)

How about the other way, i have some 45min thats old and works like 5min, how do i turn down the speed?

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## MrWillys (Mar 10, 2014)

pytlik86 said:


> How about the other way, i have some 45min thats old and works like 5min, how do i turn down the speed?
> 
> Sent from my Redmi Note 3 using Tapatalk


Mix it with 210 minute.

https://www.usg.com/content/dam/USG...-joint-compounds-easy-sand-submittal-J621.pdf


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## thefinisher (Sep 2, 2011)

pytlik86 said:


> How about the other way, i have some 45min thats old and works like 5min, how do i turn down the speed?
> 
> Sent from my Redmi Note 3 using Tapatalk


Cream of tartar may slow it down. Can get that at grocery store too!.


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## thefinisher (Sep 2, 2011)

You know USG has an alum catalyst and in their instructions it says to mix it in water and spray it onto plaster to help it set. Wonder if I can mix up some 5 or 20 minute, use half of it for first coat then spray the catalyst on it. Perhaps it would set up in time to use the rest of the same mix for the second coat...


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## Mr.Brightstar (Dec 2, 2011)

thefinisher said:


> You know USG has an alum catalyst and in their instructions it says to mix it in water and spray it onto plaster to help it set. Wonder if I can mix up some 5 or 20 minute, use half of it for first coat then spray the catalyst on it. Perhaps it would set up in time to use the rest of the same mix for the second coat...




I did that years ago as an experiment and talked about it on here. When they switched from the tub to the bag I noticed they said you could do that. I've had always wondered if they read my post or if it was just a coincidence. But I wrote it on here before it was written on the tub or bag. 

Doing patches I like to use 45 or 90. I'll put a scoop of mud on my hawk and spike The mud on my hawk with the accelerator, mix it into the mud on my hawk. It will set off in 10 to 20 minutes. Then I can double back on my patches from the original batch of mud in the bucket. 




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## Cletus (Jan 15, 2017)

take a look..never used it?
http://www.100mphmud.com/


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## endo_alley_revisited (Aug 9, 2016)

pytlik86 said:


> How about the other way, i have some 45min thats old and works like 5min, how do i turn down the speed?
> 
> Sent from my Redmi Note 3 using Tapatalk


mix it in with some plus 3.


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## pytlik86 (Sep 3, 2016)

thefinisher said:


> Cream of tartar may slow it down. Can get that at grocery store too!.


How much would u add? For 1 gallon hotmud?

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## Cletus (Jan 15, 2017)

I must have over 100 bags of 210 in my basement...gong to see how i can change the set time!
http://www.ebay.com/itm/Alum-Powder...964edb2&pid=100005&rk=3&rkt=6&sd=252778188608


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## thefinisher (Sep 2, 2011)

Love some 210 minute. Our company probably goes through 100 bags a month. As for the alum I would look for a fine powder form if you can. The stuff I used was really more like salt crystals. Needed to be dissolved in water. I do wonder what a high ratio alum mixed spray would do to mud on the wall.. would be nice to mix up a pan and spray the first coat to get it to set then use what's left in pan for 2nd coat.


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## MrWillys (Mar 10, 2014)

thefinisher said:


> Love some 210 minute. Our company probably goes through 100 bags a month. As for the alum I would look for a fine powder form if you can. The stuff I used was really more like salt crystals. Needed to be dissolved in water. I do wonder what a high ratio alum mixed spray would do to mud on the wall.. would be nice to mix up a pan and spray the first coat to get it to set then use what's left in pan for 2nd coat.


 The salt would want to burn through paint and would need to be covered by box mud or a sealer to not create sheen issues.

We used 210 to run through a gun when doing exterior applications such as parking areas.


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## Mapache Drywall (Oct 15, 2016)

Mr.Brightstar said:


> I did that years ago as an experiment and talked about it on here. When they switched from the tub to the bag I noticed they said you could do that. I've had always wondered if they read my post or if it was just a coincidence. But I wrote it on here before it was written on the tub or bag.
> 
> Doing patches I like to use 45 or 90. I'll put a scoop of mud on my hawk and spike The mud on my hawk with the accelerator, mix it into the mud on my hawk. It will set off in 10 to 20 minutes. Then I can double back on my patches from the original batch of mud in the bucket.
> 
> ...


does it work with normal air-drying compounds? and if not, why?

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## VincentRight (Nov 4, 2017)

Good info.. good tips.. thanks for the detailed explanation.. might be of help in the future.
VincentRight - Right Now www.rightnowcleaning.com


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