Coaster printing problems

I am printing Unisub coasters, and am finding some problems with cloudy/light coloured areas showing in the print.

The image below is a scan of one of my coasters with the offending white patches;

https://www.dyesubforum.co.uk/vbforu...tid=5597&stc=1

(The scan colours are off, but it does show the lighter patches.

I am printing for 65secs at 205c - as recommended on the Xpres website.

I started thinking this might be incomplete sublimation - requiring more time. However, I'm not at all sure this sis the case - and am also thinking that the relativley high temperature may be adversely affecting the blacks.

A also thought about moisture. however, I am working in a centrally heated house, so I would be surprised if this is the problem.

Could it be related to pressure? either too little, or too much?

Any thoughts would be welcome, as this is getting quite frustrating!!

You could try our setting of 190c for 75s firstly.

Up the pressure would be my guess. Shouldn't need to go over 195c or 60 secs but to high a temp wouldn't result in that print error.

My advice also. I do my coasters at 190 degrees, 55 seconds, two sheets of copy paper to soak up the moisture within the wood. Medium pressure. Too heavy and the coating will crack, too light, you'll get the patchy results.

Looks like moisture to me.

Uneven heat or pressure distribution on the press

Thanks for all your suggestion to address this issue.

Well, I have done some more experiments, and made some progress, but not fully solved yet.

To try to ensure there was no moisture on the coasters I gave them 20 seconds in the press without a transfer between a couple of sheets of copier paper.

I don't know if this helped, but it didn't see to do any harm!

I tried starting off with very little pressure, and pressing a series of coasters with increasing pressure - one turn of the handle for each coaster. I got my best results after 3.5 turns, which was a higher pressure than I was previously using.

I had been printing the transfers six to an A4 sheet, and wrapping the heat tape around the transfer paper. I guess this as a rookie mistake, and certainly not a good idea, as with the higher pressure I made a tape shaped mark on the coaster with a cloudy area around it. I am now printing four coasters to a sheet, which seems to have solved that particular problem, as I now run the heat tape flat without a fold.

During this process I ran out of my "difficult" sample print, and printed some more. I left them for a few minutes (probably about 10 minutes, maybe a little more) and then printed. The results were not as good. I think I need to leave them for quite a bit longer before printing. If my workflow allows, I think I will try to print the transfers one day, and print the coasters the next. I am using Ink Express paper and inks.

I have kept the press temperature at 195, but increased the time to 70 seconds to achieve the best level of sublimation. I will have to continue to work on this, as I feel my blacks may be turning somewhat brown. I may try reducing the temperature and increasing the time even further tomorrow to look at this.

I hope other complete newbies might find this helpful as a possible approach to dealing with this particular printing problem. There are quite a few variables to work with when trying to get good results from this process - and quite a few scrap coasters as well!!

Just to check, are you printing these white side to the heat plate? I can get coasters fully printed in 45 secs for most designs if needed. Really shouldn't need to go over 60s.

Yes I am. I did make a couple of mistakes, and virtually no ink transferred, so I just turned them over and re-pressed them. I can see a definite increase in the depth of colour in the image as I increase the time, and the residual image on the transfer paper looks lighter as the time increases. At shorter times it just doesn't look as if the colour transfer is complete. My plan for Friday is to try some alternatives reducing the time slightly with the fully dry transfer paper, and see what works best for me.

One thing I have noticed is that the quality of my prints varies depending on the image. The most tricky one is a night shot which has a lot of dark colours in the image. Lighter colour palettes appear to print successfully with slightly less pressure/ shorter times.

How do you prints end up on other blanks.... mugs etc? Also, would be worth checking the actual temp on your press. Should be fully sublimated after 50s regardless of design at that temp.

I do 9 in my press at a time and pre-press for 30 secs upside down to ensure no moisture, then i turn face up with print paper on top for 180 @ 1 min. what shows in your picture looks like what happened to me once and pre pressing helped

I have now had the chance to do some further work on this.

I think the original problem was not enough pressure. I can now get consistent coasters without the light/patchy/cloudy areas, which is a relief!

I have also come to the conclusion that the temperature readout on my heat press might be over estimating the press temperature. I thought that I might have too high a temperature, and hence browny blacks. However, as I have experimented by increasing the time and temperature the depth of the blacks has increased rather than decreased, suggesting to me now that I just wasn't getting full transfer of the dyes previously.

It seems that there are lots of variables - time, temperature, moisture, paper, ink, press, substrate etc etc, so it is necessary to keep experimenting until you can find a recipe that works for you.

Anyway, I really appreciate everyone's input. I'm sure I will have more questions as I continue to learn about this process.